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 $arg;
}
echo "Foo" . f("bar") . "Foo";
echo "\n\n";
echo "Foo", f("bar"), "Foo";
?>
The output would be:
string(3) "bar"FoobarFoo
Foostring(3) "bar"
barFoo
It would become a confusing bug for a script that uses blocking functions like sleep() as parameters:
<?php
while(true){
echo "Loop start!\n", sleep(1);
}
?>
vs
<?php
while(true){
echo "Loop started!\n" . sleep(1);
}
?>
With ',' the cursor stops at the beginning every newline, while with '.' the cursor stops after the 0 in the beginning every line (because sleep() returns 0).
echo
(PHP 4, PHP 5, PHP 7, PHP 8)
echo — Output one or more strings
Descrição
Outputs one or more expressions, with no additional newlines or spaces.
echo is not a function but a language construct.
Its arguments are a list of expressions following the echo
keyword, separated by commas, and not delimited by parentheses.
Unlike some other language constructs, echo does not have
any return value, so it cannot be used in the context of an expression.
echo also has a shortcut syntax, where you can
immediately follow the opening tag with an equals sign. This syntax is available
even with the short_open_tag configuration
setting disabled.
I have <?=$foo?> foo.
The major differences to print are that
echo accepts multiple arguments and doesn't have a return value.
Parâmetros
-
expressions -
One or more string expressions to output, separated by commas. Non-string values will be coerced to strings, even when the
strict_typesdirective is enabled.
Valor Retornado
Nenhum valor é retornado.
Exemplos
Exemplo #1 echo examples
<?php
echo "echo does not require parentheses.";
// 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.', "\n";
echo 'This ' . 'string ' . 'was ' . 'made ' . 'with concatenation.' . "\n";
// No newline or space is added; the below outputs "helloworld" all on one line
echo "hello";
echo "world";
// Same as above
echo "hello", "world";
echo "This string spans
multiple lines. The newlines will be
output as well";
echo "This string spans\nmultiple lines. The newlines will be\noutput as well.";
// The argument can be any expression which produces a string
$foo = "example";
echo "foo is $foo"; // foo is example
$fruits = ["lemon", "orange", "banana"];
echo implode(" and ", $fruits); // lemon and orange and banana
// Non-string expressions are coerced to string, even if declare(strict_types=1) is used
echo 6 * 7; // 42
// Because echo does not behave as an expression, the following code is invalid.
($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 is a valid expression, returning 1,
// so it may be used in this context.
echo $some_var ? 'true': 'false'; // evaluating the expression first and passing it to echo
?>Notas
Nota: Como esta é uma construção da linguagem e não uma função, ela não pode ser chamada usando funções variáveis ou argumentos nomeados.
Nota: Using with parentheses
Surrounding a single argument to
echowith parentheses will not raise a syntax error, and produces syntax which looks like a normal function call. However, this can be misleading, because the parentheses are actually part of the expression being output, not part of theechosyntax itself.
<?php
echo "hello";
// outputs "hello"
echo("hello");
// also outputs "hello", because ("hello") is a valid expression
echo(1 + 2) * 3;
// outputs "9"; the parentheses cause 1+2 to be evaluated first, then 3*3
// the echo statement sees the whole expression as one argument
echo "hello", " world";
// outputs "hello world"
echo("hello"), (" world");
// outputs "hello world"; the parentheses are part of each expression
echo("hello", " world");
// Throws a Parse Error because ("hello", " world") is not a valid expression
?>
Dica
Passing multiple arguments to echo can avoid
complications arising from the precedence of the concatenation operator in
PHP. For instance, the concatenation operator has higher precedence than
the ternary operator, and prior to PHP 8.0.0 had the same precedence as addition
and subtraction:
<?php
// Below, the expression 'Hello ' . isset($name) is evaluated first,
// and is always true, so the argument to echo is always $name
echo 'Hello ' . isset($name) ? $name : 'John Doe' . '!';
// The intended behaviour requires additional parentheses
echo 'Hello ' . (isset($name) ? $name : 'John Doe') . '!';
// In PHP prior to 8.0.0, the below outputs "2", rather than "Sum: 3"
echo 'Sum: ' . 1 + 2;
// Again, adding parentheses ensures the intended order of evaluation
echo 'Sum: ' . (1 + 2);If multiple arguments are passed in, then parentheses will not be required to enforce precedence, because each expression is separate:
<?php
echo "Hello ", isset($name) ? $name : "John Doe", "!";
echo "Sum: ", 1 + 2;Veja Também
- print - Mostra uma string
- printf() - Output a formatted string
- flush() - Flush system output buffer
- Ways to specify literal strings
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.";
?>
