(PHP 4, PHP 5, PHP 7)
function_exists — 锟斤拷锟斤拷锟斤拷锟斤拷暮锟斤拷锟斤拷丫锟斤拷锟斤拷锟斤拷锟酵凤拷锟斤拷 TRUE
$function_name
) : bool
锟斤拷锟窖撅拷锟斤拷锟斤拷暮锟斤拷锟斤拷斜锟斤拷锟斤拷锟较低筹拷源锟斤拷暮锟斤拷锟斤拷锟斤拷没锟斤拷远锟斤拷锟侥猴拷锟斤拷锟斤拷锟叫诧拷锟斤拷 function_name锟斤拷
function_name锟斤拷锟斤拷锟斤拷锟斤拷锟斤拷锟斤拷为一锟斤拷锟街凤拷锟斤拷锟斤拷
锟斤拷锟� function_name 锟斤拷锟斤拷锟揭碉拷确锟斤拷一锟斤拷锟斤拷锟斤拷锟酵凤拷锟斤拷 TRUE 锟斤拷锟斤拷之锟津返伙拷 FALSE 锟斤拷
Note:
锟斤拷锟斤拷锟斤法锟结构锟斤拷锟叫断ｏ拷锟斤拷锟斤拷 include_once 锟斤拷 echo 锟斤拷锟结返锟斤拷
FALSE锟斤拷
Example #1 function_exists() 锟斤拷锟斤拷锟斤拷
<?php
if (function_exists('imap_open')) {
echo "IMAP functions are available.<br />\n";
} else {
echo "IMAP functions are not available.<br />\n";
}
?>
Note:
锟斤拷锟斤拷锟斤拷锟矫伙拷锟竭憋拷锟斤拷锟斤拷锟斤拷选锟斤拷锟斤拷锟侥筹拷锟斤拷锟绞憋拷锟斤拷煤锟斤拷锟斤拷锟揭诧拷锟斤拷艽锟斤拷冢锟� image 锟斤拷锟斤拷一锟斤拷锟街成碉拷锟斤拷锟接ｏ拷