Passing multiple parameters to echo using commas (',')is not exactly identical to using the concatenation operator ('.'). There are two notable differences.
First, concatenation operators have much higher precedence. Referring to http://php.net/operators.precedence, there are many operators with lower precedence than concatenation, so it is a good idea to use the multi-argument form instead of passing concatenated strings.
<?php
echo "The sum is " . 1 | 2; // output: "2". Parentheses needed.
echo "The sum is ", 1 | 2; // output: "The sum is 3". Fine.
?>
Second, a slightly confusing phenomenon is that unlike passing arguments to functions, the values are evaluated one by one.
<?php
function f($arg){
var_dump($arg);
return $arg;
}
echo "Foo" . f("bar") . "Foo";
echo "\n\n";
echo "Foo", f("bar"), "Foo";
?>
The output would be:
string(3) "bar"FoobarFoo
Foostring(3) "bar"
barFoo
It would become a confusing bug for a script that uses blocking functions like sleep() as parameters:
<?php
while(true){
echo "Loop start!\n", sleep(1);
}
?>
vs
<?php
while(true){
echo "Loop started!\n" . sleep(1);
}
?>
With ',' the cursor stops at the beginning every newline, while with '.' the cursor stops after the 0 in the beginning every line (because sleep() returns 0).
echo
(PHP 4, PHP 5, PHP 7)
echo — Output one or more strings
Descrierea
echo
( string
$arg
, string ...$args
) : voidOutputs all parameters. No additional newline is appended.
echo is not actually a function (it is a
language construct), so you are not required to use parentheses
with it. echo (unlike some other language
constructs) does not behave like a function, so it cannot
always be used in the context of a function. Additionally, if you want to
pass more than one parameter to echo, the parameters
must not be enclosed within parentheses.
echo also has a shortcut syntax, where you can
immediately follow the opening tag with an equals sign. Prior to PHP 5.4.0,
this short syntax only works with the
short_open_tag configuration
setting enabled.
I have <?=$foo?> foo.
The major differences to print are that
echo accepts an argument list and doesn't have a return value.
Parametri
-
arg -
The parameter to output.
-
args -
Valorile întoarse
Nu este întoarsă nici o valoare.
Exemple
Example #1 echo examples
<?php
echo "Hello World";
// Strings can either be passed individually as multiple arguments or
// concatenated together and passed as a single argument
echo 'This ', 'string ', 'was ', 'made ', 'with multiple parameters.', chr(10);
echo 'This ' . 'string ' . 'was ' . 'made ' . 'with concatenation.' . "\n";
// Because echo does not behave like a function, the following code is invalid.
($some_var) ? echo 'true' : echo 'false';
// However, the following examples will work:
($some_var) ? print 'true' : print 'false'; // print is also a construct, but
// it behaves like a function, so
// it may be used in this context.
echo $some_var ? 'true': 'false'; // changing the statement around
?>
Note
Notă: Deoarece aceasta este o construcție a limbajului și nu o funcție, ea nu poate fi apelată utilizând funcții de operare cu variabile .
Sfat
A benefit to passing in multiple arguments over using concatenation in echo regards the precedence of the period operator in PHP. If multiple arguments are passed in, then parentheses will not be required to enforce precedence:
<?php
echo "Sum: ", 1 + 2;
echo "Hello ", isset($name) ? $name : "John Doe", "!";
With concatenation, the period operator has the same precedence as the addition operator, and higher precedence than the ternary operator, so parentheses must be used for the correct behaviour:
<?php
echo 'Sum: ' . (1 + 2);
echo 'Hello ' . (isset($name) ? $name : 'John Doe') . '!';
A se vedea și
- print - Output a string
- printf() - Output a formatted string
- flush() - Flush system output buffer
- Heredoc syntax
add a note
User Contributed Notes 4 notes
pemapmodder1970 at gmail dot com ¶
7 years ago
t3tesla at gmail dot com ¶
3 years ago
We can use the 'echo' shortcut syntax with the conditional operator (expr1) ? (expr2) : (expr3)
<?php
$some_var = 10;
?>
Back to html :
<p class="<?=$some_var>5 ? "class1" : "class2"?>">Some text.</p>
Will give : <p class="class1">Some text.</p>
<?php
$some_var = 4;
?>
<p class="<?=$some_var>5 ? "class1" : "class2"?>">Some text.</p>
Will give : <p class="class2">Some text.</p>
retrobytespr at mail dot com ¶
2 years ago
If you have a large block of text, say your blog or something includes code examples, you may use the <<< operator (?) to define the start and end of your block to be echoed out. For instance:
<?php
echo <<< JAVASCRIPT
function convertTroyOuncesToGrams(troyOunce) {
return troyOunce / 31.1034768;
}
JAVASCRIPT; # End of block
?>
You may also embed PHP strings and other simple scalars into your blocks of text, for example:
<?php
$troyOunceAsGrams = 31.1034768;
echo <<< JAVASCRIPT
function convertTroyOuncesToGrams(troyOunce) {
return troyOunce / {$troyOunceAsGrams};
}
JAVASCRIPT;
mparsa1372 at gmail dot com ¶
3 years ago
The following example shows how to output text with the echo command (notice that the text can contain HTML markup):
<?php
echo "<h2>PHP is Fun!</h2>";
echo "Hello world!<br>";
echo "I'm about to learn PHP!<br>";
echo "This ", "string ", "was ", "made ", "with multiple parameters.";
?>
