Description:
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ctype_alnum returns false if you pass it an integer (ie 7). I know the docs say that it should receive a string, as all ctype_* functions should, but I believe it's pointless to have to do a ctype_alnum( '' . $var ) at every call just to be sure. Also, the docs say that the function is equivalent to preg_match('/^[a-z0-9]+$/iD', $text) and matching 7 against that expression will work.

Reproduce code:
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var_dump( ctype_alnum( 7 ) );

Expected result:
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bool(true)

Actual result:
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bool(false)