Sends an error message to the web server's error log, a TCP port or to a file. The first parameter, message, is the error message that should be logged. The second parameter, message_type says where the message should go:
Table 1. error_log() log types
|message is sent to PHP's system logger, using the Operating System's system logging mechanism or a file, depending on what the error_log configuration directive is set to.
|message is sent by email to the address in the destination parameter. This is the only message type where the fourth parameter, extra_headers is used. This message type uses the same internal function as Mail() does.
|message is sent through the PHP debugging connection. This option is only available if remote debugging has been enabled. In this case, the destination parameter specifies the host name or IP address and optionally, port number, of the socket receiving the debug information.
|message is appended to the file destination.
Example 1. error_log() examples