No Parenthesis For Language Construct

print may be called without parenthesis : it, along with a small group of other PHP native structures, are called 'language construct' and are not usual functions. The language constructs are echo, print, include, include_once, require and require_once.

<?php
	print "a\n";
	print("b\n");
?>

Although both instructions behave the same, calling print with parenthesis has not the same meaning than in a function. Actually, PHP really understands the parenthesis as (sic) parenthesis, and not as arguments delimiters.

It is easier to understand the situation with the following script :

<?php

print("a") && print("b");

?>

If print was a function, then it would display a and then b. However, the script displays b1. In fact, the above script is equivalent to the one below :

<?php

print( ("a") && print("b")  );

?>

The first print function displays the result of ("a") && print "b". This expression displays "b", then return 1, and ("a") && 1 is processed, resulting in 1. At that point, the second print is actually run.

It is recommended not to use any parenthesis with language constructs, so as to avoid such pitfall.

Rule Details

List of language constructs whose parenthesis should be avoided:

• print
• echo
• include
• include_once
• require
• require_once

List of instructions whose parenthesis should be avoided too :

• return
• throw

Note that some languages constructs, such as unset, isset, empty, ... may not be used without parenthesis.

The following pattern is considered warnings:

<?php

print("a") && die()  );

?>

The following pattern are considered legit:

<?php

	// tolerated
	// print is alone in the expression
	print ("b");

	// better
	include "c";
	echo "b";
?>

When Not To Use It

If print is always used alone in the expression, there is no need to chase them all.

Further Reading

• Variable functions
• print