PHP Array Operations Summary php array usage tips

For Web programming, the most important thing is to access and read/write data. There may be many storage methods, such as strings, arrays, and files. Array is an important method in PHP Data applications. PHP has a large number of array functions. The following is a summary of my learning. I will take this note to facilitate future authentication.
1. array definition
The array definition uses the array () method to define an empty array:

The code is as follows:

$ Number = array (1, 3, 5, 7, 9 );
// Define an empty array
$ Result = array ();
$ Color = array ("red", "blue", "green ");
// Custom key value
$ Language = (1 => "English", 3 => "Chinese", 5 => "Franch ");
// Define a two-dimensional array
$ Two = array (
"Color" => array ("red", "blue"), // end with a comma
"Week" => array ("Monday", "Friday") // The last sentence contains no punctuation.
);
?>

2. create an array
Compact ()
Compact () function-converts one or more variables (including arrays) to an array: array compact (mixed $ varname [, mixed $...]).

The code is as follows:

$ Number = "1, 3, 5, 7, 9 ";
$ String = "I'm PHPer ";
$ Array = array ("And", "You? ");
$ NewArray = compact ("number", "string", "array ");
Print_r ($ newArray );
?>

The compact () function is used to convert two or more variables to an array. of course, it also contains array variables. The parameter is the variable name, not the $ full name. The opposite function is extract (). as the name suggests, it is to convert an array into a single string. The key value is used as the string name, and the array value is used as the string value.
Running result:

The code is as follows:

Array (
[Number] => 1, 3, 5, 7, 9
[String] => I'm PHPer
[Array] => Array ([0] => And [1] => You? )
)

Array_combine ()
Array_combine () -- combines two arrays into an array, one as the key value and the other as the value: array array_combine (array $ keys, array $ values)

The code is as follows:

$ Number = array ("1", "3", "5", "7", "9 ");
$ Array = array ("I", "Am", "A", "PHP", "er ");
$ NewArray = array_combine ($ number, $ array );
Print_r ($ newArray );
?>

The array_combine function is not much to talk about. everyone can understand it.
Running result:
Array ([1] => I [3] => Am [5] => A [7] => PHP [9] => er)
Range ()
Range () function -- create an array of the specified range:

The code is as follows:

$ Array1 = range (0,100, 10); // 0 indicates the start value, 100 indicates the end value, and 10 indicates the step value (the default step value is 1 ).
Print_r ($ array1 );
Echo"
";
$ Array2 = range ("A", "Z ");
Print_r ($ array2 );
Echo"
";
$ Array3 = range ("z", "");
Print_r ($ array3 );
?>

Array_fill ()
Array_fill () function -- fill array function:

The code is as follows:

$ Array = range (1, 10 );
$ Fillarray = range ("a", "d ");
$ ArrayFilled = array_fill (, $ fillarray); // $ fillarray can be a string, such as "test ".
Echo"

"; 
print_r ($arrayFilled); 
echo "

";
$ Keys = array ("string", "2", 9, "SDK", "PK ");
$ Array2 = array_fill_keys ($ keys, "testing ");
Echo"

"; 
print_r ($array2); 
echo "

";
?>

Running result:

The code is as follows:

Array
(
[0] => Array
(
[0] =>
[1] => B
[2] => c
[3] => d
)

[1] => Array
(
[0] =>
[1] => B
[2] => c
[3] => d
)

[2] => Array
(
[0] =>
[1] => B
[2] => c
[3] => d
)

[3] => Array
(
[0] =>
[1] => B
[2] => c
[3] => d
)

[4] => Array
(
[0] =>
[1] => B
[2] => c
[3] => d
)

)
Array
(
[String] => testing
[2] => testing
[9] => testing
[SDK] => testing
[PK] => testing
)

3. array traversal
Foreach traversal
Foreach (array_expression as $ value ){}
Foreach (array_expression as $ key => $ value ){}

The code is as follows:

$ Speed = array (50,120,180,240,380 );
Foreach ($ speed as $ keys => $ values ){
Echo $ keys. "=>". $ values ."
";
}
?>

Running result:
0 => 50
1 => 120
2 => 180
3 => 240
4 => 380
While loop traversal
While loop traversal is generally combined with the list function, the following is an instance

The code is as follows:

$ Staff = array (
Array ("name", "gender", "age "),
Array ("Xiao Zhang", "male", 24 ),
Array ("Wang", "female", 25 ),
Array ("Xiao Li", "male", 23)
);
Echo"

";While (list ($ keys, $ value) = each ($ staff )){List ($ name, $ sex, $ age) = $ value;Echo" ";}Echo"

$ Name

$ Sex

$ Age

";
?>

For loop traversal

The code is as follows:

$ Speed = range (0,220, 20 );
For ($ I = 0; $ I Echo $ speed [$ I]. "";
}
?>

Running result:
0 20 40 60 80 100 120 140 160 180 200
4. array pointer operation
Involved functions include reset, prev, end, next, current, and each.
Example 1: next and prev

The code is as follows:

$ Speed = range (0,220, 20 );
Echo current ($ speed); // output the value of the current position (at the beginning of the array)
$ I = rand (1, 11 );
While ($ I --){
Next ($ speed); // The pointer moves one digit backward from the current position
}
Echo current ($ speed); // output the value of the current position
Echo"
";
Echo prev ($ speed); // output the array value in the previous position
Echo"
";
Echo reset ($ speed); // reset the pointer to the starting position.
Echo"
";
Echo end ($ speed); // output the array value at the last position
Echo"
";
?>

Running result:
0220
200
0
220
Example 2: each function pointer operation

The code is as follows:

$ Speed = range (0,200, 40 );
Echo "each implement pointer move down
";
Echo "the speed of 0 blocks is". current (each ($ speed ))."
";
Echo "1 speed is". current (each ($ speed ))."
";
Echo "2 speed is". current (each ($ speed ))."
";
Echo "the speed of 3 blocks is". current (each ($ speed ))."
";
Echo "the speed of 4 blocks is". current (each ($ speed ))."
";
Echo "the speed of 5 blocks is". current (each ($ speed ))."
";
Echo "use the each function to move the array pointer and traverse the array
";
Reset ($ speed); // The array pointer points to the first part of the array.
While (list ($ key, $ value) = each ($ speed )){
Echo $ key. "=>". $ value ."
";
}
?>

Running result:

The code is as follows:

Each implements pointer moving down
The speed of 0 blocks is 0.
The speed of Block 1 is 40.
The speed of two blocks is 80.
The speed of 3 blocks is 120.
The speed of 4 blocks is 160.
The speed of the fifth gear is 200.
Use the each function to move the array pointer and traverse the array.
0 => 0
1 => 40
2 => 80
3 => 120
4 => 160
5 => 200.
5. array addition and deletion operations
Add an array member
Example 1: $ num [] = value is directly assigned to the end of the array:
[Code] $ Num = array (1 => 160 =>, 3 => );
Echo "using expressions to add array members
";
$ Num [] = 240;
Print_r ($ num );
?>

Running result:
Add Array members using expressions
Array ([0] => 80 [1] => 120 [2] => 160 [3] => 240)
Example 2: array_pad function, which selectively appends the first and end of an array

The code is as follows:

$ Num = array (1 => 160 =>, 3 => );
$ Num = array_pad ($ num, 4,200 );
Echo "use the array_pad function to add members to the end of the array.
";
Print_r ($ num );
Echo"
Array_pad can also fill the array header
";
$ Num = array_pad ($ num,-8, 40 );
Print_r ($ num );
?>

Running result:
Use the array_pad function to add members to the end of the array.
Array ([0] => 80 [1] => 120 [2] => 160 [3] => 200)
Array_pad can also fill the array header
Array ([0] => 40 [1] => 40 [2] => 40 [3] => 40 [4] => 80 [5] => 120 [6] => 160 [7] => 200)
Example 3: append an inbound stack (array_push ):

The code is as follows:

$ Num = array (1 => 160 =>, 3 => );
Array_push ($ num, 200,240,280); // You can append it by yourself and add it directly to the end of the array.
Print_r ($ num );
?>

Running result:
Array ([1] => 80 [2] => 120 [3] => 160 [4] => 200 [5] => 240 [6] => 280)
Example 4: Add an array member at the beginning of array_unshift ()

The code is as follows:

$ Num = array (1 => 160 =>, 3 => );
Array_unshift ($ num,); // You can append the value by yourself and add it directly to the end of the array.
Print_r ($ num );
?>

Running result:
Array ([0] => 0 [1] => 40 [2] => 80 [3] => 120 [4] => 160)
Note: After the array_unshift () function is used, the key value of the array starts from 0!
Delete an array member
Example 1: unset () command to delete an array member or array:

The code is as follows:

$ Num = array_fill (0, 5, rand (1, 10 ));
Print_r ($ num );
Echo"
";
Unset ($ num [4]);
Print_r ($ num );
Echo"
";
Unset ($ num );
If (is_array ){
Echo "the unset command cannot delete the entire array ";
} Else {
Echo "the unset command can delete arrays ";
}
?>

Running result: (the running error and description array are also deleted and no longer exist)
Array ([0] => 9 [1] => 9 [2] => 9 [3] => 9 [4] => 9)
Array ([0] => 9 [1] => 9 [2] => 9 [3] => 9)

Notice: Use of undefined constant is_array-assumed 'is _ array' in H: \ wamp \ www \ testing \ editorplus \ test. php on line 21
The unset command cannot delete the entire array.
Example 2: The array_splice () function deletes an array member.

The code is as follows:

$ A = array ("red", "green", "blue", "yellow ");
Count ($ a); // Get 4
Array_splice ($ a,); // deletes the second element.
Count ($ a); // Get 3
Echo $ a [2]; // obtain yellow
Echo $ a [1]; // Get blue
?>

Example 3: array_unique:

The code is as follows:

$ A = array ("red", "green", "blue", "yellow", "blue", "green ");
$ Result = array_unique ($ );
Print_r ($ result );
?>

Running result:
Array ([0] => red [1] => green [2] => blue [3] => yellow)
Example 4: array_merge and array_merge_recursive merge arrays

The code is as follows:

$ Array1 = array ("r" => "red", 1, 2, 3, 4 );
$ Array2 = array ("B" => "blue", 4 => 5, 6, 7, 8, 9 );
$ Array3 = array ("r" => "read", 4 => 10, 2 => 11 );
$ Array4 = array (
Array (4 => 10 ),
Array (7 => 13)
);
$ Array5 = array (
Array (4 => 11 ),
Array (6 => 12)
);
$ Result = array_merge ($ array1, $ array2, $ array3, $ array4, $ array5 );
Echo"

"; 
print_r($result); 
echo "

";
$ Result = array_merge_recursive ($ array1, $ array2, $ array3, $ array4, $ array5 );
Echo"

"; 
print_r ($result); 
echo "

";
?>

Running result:

The code is as follows:

Array
(
[R] => read
[0] => 1
[1] => 2
[2] => 3
[3] => 4
[B] => blue
[4] => 5
[5] => 6
[6] => 7
[7] => 8
[8] => 9
[9] => 10
[10] => 11
[11] => Array
(
[4] => 10
)

[12] => Array
(
[7] => 13
)

[13] => Array
(
[4] => 11
)

[14] => Array
(
[6] => 12
)

)
Array
(
[R] => Array
(
[0] => red
[1] => read
)

[0] => 1
[1] => 2
[2] => 3
[3] => 4
[B] => blue
[4] => 5
[5] => 6
[6] => 7
[7] => 8
[8] => 9
[9] => 10
[10] => 11
[11] => Array
(
[4] => 10
)

[12] => Array
(
[7] => 13
)

[13] => Array
(
[4] => 11
)

[14] => Array
(
[6] => 12
)

)

Note: 1. if the key name of array_merge is a number, the index will be re-created. if the same string key name is used, the subsequent key name will overwrite the previous one. 2. the array_merge_recursive function integrates the key list elements of the same string into an array.
6. array key value and value operations
Example 1: in_array () checks whether a value exists in the array.

The code is as follows:

$ Array = range (0, 9 );
If (in_array (9, $ array )){
Echo "exists in the array ";
}
?>

Running result: an array exists.
Example 2: key () gets the current key name of the array:

The code is as follows:

$ Array = range (0, 9 );
$ Num = rand (0, 8 );
While ($ num --)
Next ($ array );
$ Key = key ($ array );
Echo $ key;
?>

The result of this instance is a dynamic result in the range of (0-8) and is not displayed.
Example 3: The list () function assigns the values in the array to the specified variable:

The code is as follows:

$ Staff = array (
Array ("name", "gender", "age "),
Array ("Xiao Zhang", "male", 24 ),
Array ("Wang", "female", 25 ),
Array ("Xiao Li", "male", 23)
);
Echo"

";While (list ($ keys, $ value) = each ($ staff )){List ($ name, $ sex, $ age) = $ value;Echo" ";}Echo"

$ Name

$ Sex

$ Age

";
?>

Example 4: array_flip () swap the key value and value of the array:

The code is as follows:

$ Array = array ("red", "blue", "yellow", "Black ");
Print_r ($ array );
Echo"
";
$ Array = array_flip ($ array );
Print_r ($ array );
?>

Running result:
Array ([0] => red [1] => blue [2] => yellow [3] => Black)
Array ([red] => 0 [blue] => 1 [yellow] => 2 [Black] => 3)

The code is as follows:

$ Array = array ("red", "blue", "yellow", "Black ");
$ Result = array_keys ($ array );
Print_r ($ result );
Echo"
";
$ Result = array_values ($ array );
Print_r ($ result );
?>

Running result:
Array ([0] => 0 [1] => 1 [2] => 2 [3] => 3)
Array ([0] => red [1] => blue [2] => yellow [3] => Black)
Example 6: array_search () search value:

The code is as follows:

$ Array = array ("red", "blue", "yellow", "Black ");
$ Result = array_search ("red", $ array );
If ($ result = NULL )){
Echo "no value red ";
} Else {
Echo "value $ result ";
}
?>

Result: a value of 0 exists.
The value returned by the array_search () function may be false, 0, or NULL. therefore, be sure to use "=" when determining the value"
7. sort arrays
Example 1: sorting arrays by sort (), rsort ()/asort (), and arsort:

The code is as follows:

$ Array = array ("B", "c", "d", "");
Sort ($ array); // sort from low to high
Print_r ($ array );
Echo"
";
Rsort ($ array); // reverse sorting
Print_r ($ array );
?>

Result:
Array ([0] => a [1] => B [2] => c [3] => d)
Array ([0] => d [1] => c [2] => B [3] =>)
The sort () and rsort () functions sort arrays in ascending order and return bool values;
The asort () and arsort () functions retain the sorting of key values. after sorting, the key values are not re-indexed.
Example 2: disrupt the array order -- shuffle () function:

The code is as follows:

$ Array = array ("a", "B", "c", "d ");
Shuffle ($ array); // sort from low to high
Print_r ($ array );
?>

The result is dynamic:
Array ([0] => c [1] => a [2] => d [3] => B)
The shuffle result is a bit random, and each refresh is different.
Example 3: reverse direction of the array_reverse () array:

The code is as follows:

$ Array = array ("d", "B", "a", "c ");
$ Array = array_reverse ($ array); // sort from low to high
Print_r ($ array );
?>

Running result:
Array ([0] => c [1] => a [2] => B [3] => d)
Example 4: Natural sorting algorithms natsort () and natcasesort ();

The code is as follows:

$ Array = array ("sort2", "Sort5", "sort1", "sort4 ");
Natsort ($ array); // sort from low to high
Print_r ($ array );
Echo"
";
Natcasesort ($ array );
Print_r ($ array );
?>

Result:
Array ([1] => Sort5 [2] => sort1 [0] => sort2 [3] => sort4)
Array ([2] => sort1 [0] => sort2 [3] => sort4 [1] => Sort5)
Natsort () and natcasesort () are used to sort arrays in a natural way. Natcasesort ignores case sensitivity.
Example 5: sort the key values of the array ksort ():

The code is as follows:

$ Array = array (1 => "sort2", 4 => "Sort5", 2 => "sort1", 3 => "sort4 ");
Ksort ($ array); // sort from low to high
Print_r ($ array );
?>

Result:
Array ([1] => sort2 [2] => sort1 [3] => sort4 [4] => Sort5)
Note: The ksort () function re-creates an index.
8. other array usage

The code is as follows:

Cout ($ array) -------- count the number of units in the array
Array_diff ($ array1, $ array2) ---------- calculate the differences between arrays, and return the results that are included in the first array but not in the second array.
Array_diff_assoc ($ array1, $ array2) --------- Same as array_diff (), but it only compares key values
Array_diff_key ($ array1, $ array2) ---------- compare key values
Array_product ($ array) ----------- returns the product of all numbers in the array.
Array_sum ($ array) ------------ sum of all values
Array_rand ($ array, $ n) ---------- in the $ array, get $ n values and return the array
Array_intersect ($ array1, $ array2) -------------- get the intersection of two arrays
Array_intersect_assoc ($ array1, $ array2) ------------- perform key value comparison based on array_intersect
Array_intersect_key ($ array1, $ array2) --------------- compare the intersection of the key values of the two arrays

Summary
The use of arrays is crucial in PHP. because PHP does not have pointers, arrays undertake a large amount of data operation tasks. Learning arrays well can make PHP applications handy. all the functions and usage related to PHP arrays are listed here. please study them together!