A useful error logging function intended for use with WordPress. Simply add to your wp-config.php, or other non-version controlled PHP file.

pj_error_log.function.php

<?php
if ( ! defined( 'PJID' ) ) define( 'PJID', uniqid() );
function pj_error_log(){

	// Get line numbers and such
	$bt = debug_backtrace();
	$caller = array_shift($bt);

	// First we check if we're being asked to print a pretty message
	if ( func_num_args() == 2 && is_string( func_get_arg(0) ) ) {
		$msg = array(
			PJID,
			'L' . $caller['line'],
			func_get_arg(0),
			':',
			var_export( func_get_arg(1), true ),
		);

		// Do the message
		error_log( implode( ' ', $msg ) );

	}

	else {

		// Otherwise, just print each message/var accordingly.
		foreach ( func_get_args() as $arg ) {

			// Add the ID to our message
			$msg = array( PJID );

			// and the line number
			$msg[] = 'L' . $caller['line'];

			// This is just a string, so chuck it straight out.
			if ( is_string( $arg ) )
				$msg[] = $arg;
			else // a variable, so var_export it
				$msg[] = var_export( $arg, true );

			// Do the message
			error_log( implode( ' ', $msg ) );

		}

	}

}
?>