How can I remove three characters at the end of a string in PHP?

Just do:

echo substr($string, 0, -3);

You don't need to use a strlen call, since, as noted in the substr documentation:

If length is given and is negative, then that many characters will be omitted from the end of string

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<?php echo substr("abcabcabc", 0, -3); ?>

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<?php echo substr($string, 0, strlen($string) - 3); ?>

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