Let str_replace effect one time

<?php
$names="my site your site not their site";

$a1 = str_replace("site", "<a href='http://forums.digitalpoint.com'>site</a>", "$names");

echo $a1;
?> 

PHP:

result:

----------

how to let str_replace effect one time?

i would like below result

thank you

 

PHP documentation says:
str_replace — Replace all occurrences of the search string with the replacement string

So, to replace only one occurrence you need another way, another function:
preg_replace

<?php
$names="my site your site not their site";

$a1 = str_replace("site", "<a href='http://forums.digitalpoint.com'>site</a>", "$names");
echo $a1;

echo "<br /><br /><br />";
$a1 = preg_replace("/site/", "<a href='http://forums.digitalpoint.com'>site</a>", "$names", 1);
echo $a1;
?>

PHP:

 

It's working
thank you so much bitist