Be careful when using print. Since print is a language construct and not a function, the parentheses around the argument is not required.
In fact, using parentheses can cause confusion with the syntax of a function and SHOULD be omited.
Most would expect the following behavior:
<?php
if (print("foo") && print("bar")) {
// "foo" and "bar" had been printed
}
?>
But since the parenthesis around the argument are not required, they are interpretet as part of the argument.
This means that the argument of the first print is
("foo") && print("bar")
and the argument of the second print is just
("bar")
For the expected behavior of the first example, you need to write:
<?php
if ((print "foo") && (print "bar")) {
// "foo" and "bar" had been printed
}
?>
(PHP 4, PHP 5, PHP 7, PHP 8)
print — Affiche une chaîne de caractères
Description
Affiche expression.
print n'est pas une fonction mais une construction du langage.
Son argument est l'expression suivant le mot clé print,
et n'est pas délimité par des parenthèses.
La différence majeure avec echo est que
print n'accepte qu'un seul argument et retourne toujours 1.
Liste de paramètres
-
expression -
L'expression à afficher. Les valeurs qui ne sont pas des chaînes de caractères seront converties en celle-ci, même si la directive
strict_typesest activé.
Valeurs de retour
Retourne 1, toujours.
Exemples
Exemple #1 Exemple avec print
<?php
print "print does not require parentheses.";
// No newline or space is added; the below outputs "helloworld" all on one line
print "hello";
print "world";
print "This string spans
multiple lines. The newlines will be
output as well";
print "This string spans\nmultiple lines. The newlines will be\noutput as well.";
// The argument can be any expression which produces a string
$foo = "example";
print "foo is $foo"; // foo is example
$fruits = ["lemon", "orange", "banana"];
print implode(" and ", $fruits); // lemon and orange and banana
// Non-string expressions are coerced to string, even if declare(strict_types=1) is used
print 6 * 7; // 42
// Because print has a return value, it can be used in expressions
// The following outputs "hello world"
if ( print "hello" ) {
echo " world";
}
// The following outputs "true"
( 1 === 1 ) ? print 'true' : print 'false';
?>Notes
Note: Utilisation avec des parenthèses
Entourer l'argument de
<?php
print "hello";
// outputs "hello"
print("hello");
// also outputs "hello", because ("hello") is a valid expression
print(1 + 2) * 3;
// outputs "9"; the parentheses cause 1+2 to be evaluated first, then 3*3
// the print statement sees the whole expression as one argument
if ( print("hello") && false ) {
print " - inside if";
}
else {
print " - inside else";
}
// outputs " - inside if"
// the expression ("hello") && false is first evaluated, giving false
// this is coerced to the empty string "" and printed
// the print construct then returns 1, so code in the if block is run
?>Quand
<?php
if ( (print "hello") && false ) {
print " - inside if";
}
else {
print " - inside else";
}
// outputs "hello - inside else"
// unlike the previous example, the expression (print "hello") is evaluated first
// after outputting "hello", print returns 1
// since 1 && false is false, code in the else block is run
print "hello " && print "world";
// outputs "world1"; print "world" is evaluated first,
// then the expression "hello " && 1 is passed to the left-hand print
(print "hello ") && (print "world");
// outputs "hello world"; the parentheses force the print expressions
// to be evaluated before the &&
?>
Note: Comme ceci est une structure du langage, et non pas une fonction, il n'est pas possible de l'appeler avec les fonctions variables ou arguments nommés.
Voir aussi
- echo - Affiche une chaîne de caractères
- printf() - Affiche une chaîne de caractères formatée
- flush() - Vide les tampons de sortie du système
- Manière de spécifié des chaînes littérales
add a note
User Contributed Notes 3 notes
user at example dot net ¶
16 years ago
danielxmorris @ gmail dotcom ¶
16 years ago
I wrote a println function that determines whether a \n or a <br /> should be appended to the line depending on whether it's being executed in a shell or a browser window. People have probably thought of this before but I thought I'd post it anyway - it may help a couple of people.
<?php
function println ($string_message) {
$_SERVER['SERVER_PROTOCOL'] ? print "$string_message<br />" : print "$string_message\n";
}
?>
Examples:
Running in a browser:
<?php println ("Hello, world!"); ?>
Output: Hello, world!<br />
Running in a shell:
<?php println ("Hello, world!"); ?>
Output: Hello, world!\n
mark at manngo dot net ¶
1 year ago
The other major difference with echo is that print returns a value, even it’s always 1.
That might not look like much, but you can use print in another expression. Here are some examples:
<?php
rand(0,1) ? print 'Hello' : print 'goodbye';
print PHP_EOL;
print 'Hello ' and print 'goodbye';
print PHP_EOL;
rand(0,1) or print 'whatever';
?>
Here’s a more serious example:
<?php
function test() {
return !!rand(0,1);
}
test() or print 'failed';
?>
