Description:
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preg_grep should capture subpatterns.  Currently it doesn't have the ability to do this.  

Reproduce code:
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array preg_grep ( string pattern, array input [, int flags] )

Expected result:
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The return array would return a two dimensional array if you set a flag like PREG_GREP_CAPTURE.  $array[n][0] would be the fully captured string and each additional index in that dimension would return the subpattern matches.

Example:

<?php
$arrInput = array('5741234-5671','5741235','5741236-432');
$arrMatches = preg_grep('/([2-9][0-9]{6,15})(?:\-([0-9]{2,6}))?/', $arrInput, PREG_GREP_CAPTURE);
?>

Content of $arrMatches:

$arrMatches[0][0] = '5741234-5671'
$arrMatches[0][1] = '5741234'
$arrMatches[0][2] = '5671'
$arrMatches[1][0] = '5741235'
$arrMatches[2][0] = '5741236-432'
$arrMatches[2][1] = '5741236'
$arrMatches[2][2] = '432'

Actual result:
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array preg_grep ( string pattern, array input [, int flags] )