PHP Basics: Array definition and traversal

Array definition: Number of arrays a composite data, to use Print_r to print, you can load a number of values, each value with a different key to distinguish, (keys and values to correspond to each other), the key = the number on the box, the value of the box contents such as: $a = array (a=> ' Zhansan ',b=> ' Lisi ',c=> ' Wanglu '); Print_r ($a);

Additions and deletions of array elements
$a = array (1=> ' php ',2=> ' html ',3=> ' CSS ',4=> ' MySQL ', 5=>array (' a ' + = ' ajax ', ' b ' = ' jquery '));
Remove a value individually
echo $a [1];
Take out a two-dimensional array of value arrays up to 3 levels otherwise people can't understand.
echo $a [5][b];
Change the value of an array cell
$a [5][' a ']=linux;
Print_r ($a);
Add a unit
$a [6] = ' git ';
Delete an array cell
unset ($a [6]);
Print_r ($a);

Iterating through an array
Take out all the values in the array
$a = Array (' A ', ' B ', ' C ', ' d ', ' e ');
echo $a [0];
echo $a [1];
echo $a [2];

The loop index array can be so//count () that the number of elements in the array is computed.
for ($b =0; $b <count ($a); $b + +) {
echo $a [$b], ' <br/> ';} //

Traversing all values in an associative array
foreach ($a as $k = = $v);
Echo $k, ': ', $v, ' <br/> ';

Loop-only key Array_keys (): Returns all the key names in the array. There is no way for a foreach to loop out the key name in a single value,

All values are traversed in the associative array.
foreach ($a as $k = = $v) {
echo $a [$k] = $v, ' <br/> ';
}

Title: $stu = Array (' Lisi ' =>3, ' Wang ' =>5, ' Zhao ' =>6); Change the value of this array to twice times the original
foreach ($stu as $k = = $v) {
echo $stu [$k] = $v * *;
}
Print_r ($stu);

/* $arr = Array (' name ' = ' Lisi ', ' name1 ' = ' zhangsan ', ' name2 ' =>array (' name3 ' = ' ctx ', ' age ' = ' 18 '));
foreach ($arr as $k = + $v) {
    echo $k. ' ~ '. $v, ' <br/> ';
}
//How to loop out the see and value of the two-dimensional array */

/* $array = Array (1=> ' a ',2=> ' B ',3=> ' C ',4=> ' d ');
for ($i =1; $i <count ($array), $i + +) {
    echo $array [$i];
}
foreach ($array as $k = + $v) {
    echo $k. ' ~ '. $v, ' <br/> ';
} */

$array = Array (1=> ' a ',2=> ' B ',3=> ' C ',4=> ' d ');
/*foreach ($array as $k = + $v) {
    echo $v, ' <br/> ';
} The
//array does not have a way to loop out the keys separately
*/
/*print_r (Array_keys ($array));//array_keys This function is to take out all the keys in the number cell */

$stu = array (' Lisi ' =>3, ' Wanwu ' =>5, ' Zhaoliu ' =>6);
foreach ($stu as $k + $v) {
    $stu [$k] = $v *2;//Here's to note that this is a cell that modifies an array, so to modify the array cell format
}
Print_r ($stu);

$arr = Array (' name1 ' = ' lisi ', ' name2 ' = ' zhansan ', ' Name3 ' =>array (' name ' = ' = ' Wangwu ', ' age ' =>28, ' Genden ' = ' + ' man ');
Print the entire array
Print_r ($arr);
Echo ' <br/> ';

Take an array unit
Print_r ($arr [' name1 ']);

Echo ' <br/> ';

Take a unit of a two-dimensional array
Print_r ($arr [' Name3 '] [' Genden ']);
Echo ' <br/> ';

Modifying an array cell
$arr [' name1 '] = ' ctx ';
Print_r ($arr);
Echo ' <br/> ';
$arr [' Name3 '] [' age '] = 18;
Print_r ($arr);
Echo ' <br/> ';

Add an array unit
$arr [' name4 '] = ' ctxryqdnz ';
Print_r ($arr);
Echo ' <br/> ';

$arr [' Name3 '] [' height '] = 185;
Print_r ($arr);
Echo ' <br/> ';

Delete an array cell
unset ($arr [' name4 ']);
Print_r ($arr);
Echo ' <br/> ';
unset ($arr [' Name3 '] [' height ']);
Print_r ($arr);

PHP Basics: Array definition and traversal