PHP Regular Expressions Summary of common functions (code example)

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Regular expression functions commonly used in PHP
* Preg_match ()
* Preg_match_all ()
* Preg_replace ()
* Preg_filter ()
* PREG_GREP ()
* Preg_split ()
* Preg_quote ()

The following comparison explains:

$pattern usually regular expressions $subject usually represent the target processing data
Define a method for easy viewing of data types:

Function Show ($val = null) {    if (empty ($val)) {            //print empty        echo ' Mull ';    } ElseIf (Is_array ($val) | | is_object ($val)) {            //print array or object        echo ' <pre> ';        Print_r ($val);                Echo ' </pre> ';    } else{            //print string int float        echo $val;    }}

1. Preg_match () and Preg_match_all ()

  /* Method Simple Description */  Preg_match ($pattern, $subject, [array & $matches])    //Match once  third parameter optional  match result place matches array  Preg_match_all ($pattern, $subject, array &matches)   //Match multiple  three-parameter required      match results place the matches array  $pattern = '/[0-9]/';  $subject = ' b5fg4sgf3sd2f1g ';  $m 1 =preg_match ($pattern, $subject, $arr 1), Show ($m 1), Show ($arr 1),/* 1Array (    [0] = 5) */$m 2 =preg_match_all ($ Pattern, $subject, $arr 2), Show ($m 2), Show ($arr 2),/* 5Array (    [0] = = Array        (            [0] = 5            [1] = = 4            [2] = 3            [3] = 2            [4] = 1        )) */

2.preg_replace () and Preg_filter ()

/* Method Simple Description *//* * * preg_replace and Preg_filter * preg_replace ($pattern, $replacement, $subject) *//Regular replacement function is replaced by an array of objects is returned all// The regular replacement function is replaced by an array of objects that are returned only by the substituted element * Lenovo: Str_repalce () * Echo Str_replace ("World", "Shanghai", "Hello world!"); *//Get Hello shanghai!//replace string in first Test string conclusion: here Preg_replace () and Preg_filter () no difference $pattern = '/[0-9]/'; $subject = ' b65fg4sgf3sd2f1g '; $replacement = ' _ '; $str 1 = preg_replace ($pattern, $replacement, $subject); $str 2 = Preg_filter ($ Pattern, $replacement, $subject); Echo ' 

3. Preg_grep ($pattern, array $subject)//Here $subject can only be a one-dimensional array

/* Function Description */preg_grep ($pattern, array $input)//can only match one-dimensional array return matching successful array elements can be understood Preg_grep () for the castrated version of Preg_filter () only did the match do not replace $pattern = '/[0-9]/'; $subject =array (' B ', ' fg3 ', ' 456 ', ' SGF ', ' 789 ', ' FG '); $arr = Preg_grep ($pattern, $subject); show ($arr);/* Array (    [1] = Fg3    [2] = 456    [4] = 789) */

4. Preg_split ($pattern, $subject)//A match successfully cuts the string for the cutting point array
can understand Preg_split () upgraded version of Explode ()

$pattern = '/[0-9]/'; $subject = ' BFG3456SGF789FG '; $arr = Preg_split ($pattern, $subject); show ($arr);/*array (    [0] = > BFG    [1] =    [2] = [3] = [    4] = SGF    [5] =    [6] =    [7] = FG) */

5. Preg_quote ($STR) regular operator translation

/* * Preg_quote ($STR) The regular operator translates *  . \ + *? [ ^ ] $ () {} = ! < > | :-* * */echo ' 

Simple summary of the continuity:
Preg_ Opening
Except for the Preg_quote function, the first argument is a regular expression
Preg_match form validation, etc.
Preg_replace illegal word filter, etc.