preg_filter

(PHP 5 >= 5.3.0, PHP 7, PHP 8)

preg_filter — Perform a regular expression search and replace

Descrizione

preg_filter() is identical to preg_replace() except it only returns the (possibly transformed) subjects where there was a match. For details about how this function works, read the preg_replace() documentation.

Elenco dei parametri

Parameters are described in the documentation for preg_replace().

Valori restituiti

Returns an array if the subject parameter is an array, or a string otherwise.

If no matches are found or an error occurred, an empty array is returned when subject is an array or null otherwise.

Errori/Eccezioni

If the regex pattern passed does not compile to a valid regex, an E_WARNING is emitted.

Esempi

Example #1 Example comparing preg_filter() with preg_replace()

<?php
$subject = array('1', 'a', '2', 'b', '3', 'A', 'B', '4'); 
$pattern = array('/\d/', '/[a-z]/', '/[1a]/'); 
$replace = array('A:$0', 'B:$0', 'C:$0'); 

echo "preg_filter returns\n";
print_r(preg_filter($pattern, $replace, $subject)); 

echo "preg_replace returns\n";
print_r(preg_replace($pattern, $replace, $subject)); 
?>

Il precedente esempio visualizzerà:

preg_filter returns
Array
(
    [0] => A:C:1
    [1] => B:C:a
    [2] => A:2
    [3] => B:b
    [4] => A:3
    [7] => A:4
)
preg_replace returns
Array
(
    [0] => A:C:1
    [1] => B:C:a
    [2] => A:2
    [3] => B:b
    [4] => A:3
    [5] => A
    [6] => B
    [7] => A:4
)

Vedere anche:

PCRE Patterns
preg_quote() - Inserisce il carattere di escape nei caratteri delle espressioni regolari
preg_replace() - Esegue una ricerca ed una sostituzione con le espressioni regolari
preg_replace_callback() - Esegue ricerche e sostituzioni con espressioni regolari usando una callback
preg_grep() - Restituisce una matrice degli elementi riconosciuti tramite le espressioni regolari
preg_last_error() - Returns the error code of the last PCRE regex execution

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User Contributed Notes 3 notes

down

forsoap at gmail dot com ¶

8 years ago

For those who read manual not in English and figure out that example code returns not the same result as in documentation

You need put in example patter modifier "u" to get same result:

<?php
$subject = array('1', 'а', '2', 'б', '3', 'А', 'Б', '4');
// Added "u"
$pattern = array('/\d/u', '/[а-я]/u', '/[1а]/u');
$replace = array('А:$0', 'Б:$0', 'В:$0');
?>

down

bienvenunet at yahoo dot com ¶

7 years ago

If you don't want to actually replace the matches, just filter the array to them, make the replacement parameter '$0'.

<?php
$subject = array('1', 'a', '2', 'b', '3', 'A', 'B', '4'); 
$result = preg_filter('/\d/', '$0', $subject);  // ['1','2','3','4']
?>

down

sajina_99 at hotmail dot de ¶

13 years ago

As I had to work with PHP5.2.X and needed preg_filter I wrote a quick and dirty workaround.

<?php
  if (!function_exists('preg_filter')) {
  
    function preg_filter($pattern, $replace, $subject, $limit = -1 , &$count = null) {
    
      if(!is_array($subject)) {
        $noArray = 1 ;
        $subject = array($subject);
      }

      $preg = preg_replace($pattern, $replace, $subject, $limit,  &$count);

      $diff = array_diff($preg, $subject);
      
      if($noArray == 1) $diff = implode($diff) ;

      return $diff ;
      
    }
    
  }
?>

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