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(PHP 3>= 3.0.7, PHP 4 )

function_exists -- Return true if the given function has been defined


bool function_exists (string function_name)

Checks the list of defined functions for function_name. Returns true if the given function name was found, false otherwise.

if (function_exists('imap_open')) {     echo "IMAP functions are available.<br>\n"; } else {     echo "IMAP functions are not available.<br>\n"; }       

Note that a function name may exist, even if the function itself is unusable due to configuration or compiling options.

See also method_exists().