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  1. <?php 
  2.     $st = '2'; 
  3.     $p = '#'.$st.'#'; 
  4.     $r = '___RPLCMNT___'; 
  5.     $s = 'вывыаыва2ываываыва2ыаыаываы2пвпва';
  6.  
  7.     //например так. если не нужны regexp, то strrpos()
  8.     $ps = preg_split($p,$s,-1, PREG_SPLIT_OFFSET_CAPTURE);
  9.  
  10.     $pos = $ps[count($ps)-1][1];
  11.     $rs = substr_replace($s, $r, $pos-strlen($st), -(strlen($s)-$pos));
  12.  
  13.     echo $s.' ==> '.$rs;    
  14. ?>
Success #stdin #stdout 0.01s 20568KB
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вывыаыва2ываываыва2ыаыаываы2пвпва ==> вывыаыва2ываываыва2ыаыаываы___RPLCMNT___пвпва
https://ideone.com/TPECgZ
language:
PHP (php 7.3.5)
created:
12 years ago
visibility:
secret

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