PHP str_replace

Question

I have the string $var in which I need to replace some text. The first \"X\" needs to be replaced by \"A\", the second \"X\" needs to be replaced by B and so on, here is an exam

Answer 1

$var = 'X X X X';
$replacements = array('A', 'B', 'C', 'D');

$var = preg_replace_callback('/X/', function() use (&$replacements) {
    return array_shift($replacements);
}, $var);

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Other solution:

$var = preg_replace('/X/', 'A', $var, 1);
$var = preg_replace('/X/', 'B', $var, 1);
$var = preg_replace('/X/', 'C', $var, 1);
$var = preg_replace('/X/', 'D', $var, 1);

This one uses the $limit parameter of preg_replace (we replace only one occurrence per call).