PHP Collation (i): Variables and strings

Variables in PHP:

1. Define: $ symbol to define the variable

2. Description:

(1) PHP weak language, when defining variables without declaring the type, but does not mean that PHP does not have a data type

(2) Variable names are case-sensitive and can only be numbers, letters, or underscores

(3) The variable defaults to the value assignment, which means that two variables are completely independent after the assignment

$a = "string"; $b = $a; Pass the value over, there is no effect between $a and $b

(4) PHP also provides another way to assign a value----a reference assignment, when you pass an address

<?php$foo  =  ' Bob ';               Assign ' Bob ' to $foo $bar  = & $foo;               by $bar reference $foo $bar  =  "My name is  $bar";   Modify $bar variable echo  $bar; echo  $foo;                  The value of the $foo is also modified?>

(5) Globle $a; Used to define global variables, used in function body (the function body does not call global variables by default)

String in PHP:

1. Definition: Double quotation marks ("") and single quotation marks (') to define a string

"String" (double quotation marks):

(1) PHP will parse some special characters (escape characters)

(2) Variables in string form will also be parsed

$str = 1;echo "This is a {$str} string";

Results:

This is a string of 1

' String ' (single quote):

Just a simple string with no corresponding parsing capability

2. Common methods

(1) String length: strlen (String);

$str = "I am a string"; Echo strlen ($STR);

Operation Result:

13

(2) Comparison string: strcmp (string1,string2)----case-sensitive, return 0 (same) and 1 (not the same); STRCASECMP (STRING1,STRING2);----case insensitive, returns 0 (same) and 1 (not the same)

$str = "I am a string"; $str _1= "I am a string"; Echo strcmp ($str, $str _1);//Case-sensitive echo "<br/>"; Echo strcasecmp ($str, $st r_1);//Case insensitive

Operation Result:
1 (different)
0 (same)

(3) Convert case: Strtolower (String),----to lowercase, strtoupper (string),----to uppercase;

1 $str = "I am a string", 2 $str _1= "I am a string", 3 echo strtolower ($STR), 4 echo "<br/>", 5 echo strtoupper ($str _1);

Splitting and merging strings explode (delimiter,string[,limit]); implode ([Glue,]array);

1 $str = "I am A String", 2 $arr =explode ("", $str), 3 Print_r ($arr), 4 echo "<br/>", 5 echo Implode ("", $arr);

Operation Result:

Array ([0] = I [1] = AM [2] = a [3] = = string)
I am a String

(4) Interception of replacement Substr_replace (String,replacement,start_index[,length]);

If replacement is an empty string, there is a substitution meaning. Precise control can be achieved by starting position and length; If replacement is not an empty string, it replaces the

1 $str = "I am A String", 2 echo $str, 3 echo "<br/>", 4 echo substr_replace ($str, "#", 3),//replaces the 3 to the last character 5 echo "<br/& gt; "; 6 echo substr_replace ($str, "#", 3,5);//Replace the string 7 echo "<br/>" from 3 (including 3) 5 lengths, 8 Echo substr_replace ($str, "", 0,7);// Truncated string string

Operation Result:

I am a String
I a#
I a#tring
String

(5) Find alternate array and string Str_replace (search,replacement,string[, $count]); $count returns the number of replacements

1//Assignment: Body text= ' black ' 2 $bodytag  =  str_replace ("%body%",  "Black",  "body1 text= '%body% '"); 3 echo $bodytag; 4 echo "<br/>"; 5  6//assignment: Hll wrld F PHP 7 $vowels  = Array ("A",  "E",  "I",  "O",  "U",  "a",  "E", 
     "I",  "O",  "U"), 8 $onlyconsonants  =  str_replace ($vowels, "  ",  "Hello World of PHP" ); 9 echo $onlyconsonants, echo "<br/>", 11 12//assignment: You should eat pizza, beer, and ice cream every day13 $phrase 
    =  "You should eat fruits, vegetables, and fiber every day." $healthy  = Array ("Fruits",  "vegetables ",  " fiber "); $yummy    = Array (" Pizza ",  " beer ",  " ice Cream "), $newphrase  =  str_re Place ($healthy,  $yummy,  $phrase); echo $newphrase; echo "<br/>"; 20 21//Assignment: 222 $str  =
    
     str_replace ("ll", "  ", "  Good Golly Miss molly!",  $count); Echo  $count;
    

(6) Intercept substr (String,start_index[,length]); Strat_index and length can be negative, search in the opposite direction

1 echo substr ("ABCdef",-1);//Includes Start_index's position 2 echo "<br/>"; 3 echo substr ("ABCdef", 5); 4 echo "<br/>"; 5 echo substr ("ABCdef", 2); 6 echo "<br/>"; 7 echo substr ("ABCDE", 1,4),//length length, when positive 8 echo "<br/>"; 9 echo substr ("ABCDE", 0,-1);//abcde, ending at 1 from the end of the string echo "<br/>"; Echo substr ("ABCDE", 1,-2);//BC

Regular Expressions in PHP:

1. Definition://

2. Method:

int  preg_match   ( string  $pattern  , string  $subject  [, array & $matches  [,  int  $flags  = 0 [,  int $ Offset  = 0]])----Replace qualified, default is global, limit number of times can be used

preg_match () returns pattern the number of matches. Its value will be 0 times (mismatched) or 1 times, because preg_match () will stop the search after the first match. Preg_match_all () differs from this, and it searches subject until the end is reached.

1 echo preg_replace ($pattern, "#", $str), 2 echo "<br/>", 3 echo preg_replace ($pattern, "#", $str, 1, $c); 4 echo "<br /> ";

Results:

# ## # ######!
# AM a string!

Preg_split (preg,string);----Split by Preg, returns an array

1 $str = "I am a string!"; 2 $pattern = "//"; 3 Print_r (Preg_split ($pattern, $str));

Results:

Array ([0] = [1] = I [2] = = [3] = a [4] = = m [5] = [6] = a [7] = = [8] = S [9] = [1] 0] = = r [One] = I [n] ~ ~ [+] = g [+] =! [+] =)

　　　Mixed preg_replace ( mixed $pattern , mixed $replacement , mixed $subject [, int $limit =-1 [, int &$count ]])

　　　Array preg_grep ( string $pattern , array $input [, int $flags = 0])

Returns an array of elements in the given array that input pattern match the pattern.

Functions in PHP:

Definition: Function name () {};

Note: Return values and Parameters

Parameters: Can be many, not less

Func_get_args (): Returns an array that contains all the arguments

Func_num_args (): Returns the number of parameters

PHP Collation (i): Variables and strings