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 — Exibe uma ou mais strings
Descrição
void echo
( string
$arg1
[, string $...
] )Exibe todos os parâmetros.
echo não é uma função atualmente (construtor da linguagem) então não é obrigatório usar parênteses. echo (diferente de outro construtor da linguagem) não se comporta como uma função, então ele nem sempre é usado no contexto de uma função. Sendo assim, se você quer passar mais de um parâmetro para echo, os parâmetros não precisam estar entre parênteses.
echo também tem um sintaxe curta, onde você pode imediatamente abrir a tag com o sinal de igual. Esta sintaxe curta funciona habilitando a definição da configuração short_open_tag.
I have <?=$foo?> foo.
Parâmetros
-
arg1 -
O parâmetro a exibir.
-
... -
Valor Retornado
Não há valor retornado.
Exemplos
Exemplo #1 echo exemplos
<?php
echo "Hello World";
echo "This spans
multiple lines. The newlines will be
output as well";
echo "This spans\nmultiple lines. The newlines will be\noutput as well.";
echo "Escaping characters is done \"Like this\".";
// You can use variables inside of an echo statement
$foo = "foobar";
$bar = "barbaz";
echo "foo is $foo"; // foo is foobar
// You can also use arrays
$baz = array("value" => "foo");
echo "this is {$baz['value']} !"; // this is foo !
// Using single quotes will print the variable name, not the value
echo 'foo is $foo'; // foo is $foo
// If you are not using any other characters, you can just echo variables
echo $foo; // foobar
echo $foo,$bar; // foobarbarbaz
// Some people prefer passing multiple parameters to echo over concatenation.
echo 'This ', 'string ', 'was ', 'made ', 'with multiple parameters.', chr(10);
echo 'This ' . 'string ' . 'was ' . 'made ' . 'with concatenation.' . "\n";
echo <<<END
This uses the "here document" syntax to output
multiple lines with $variable interpolation. Note
that the here document terminator must appear on a
line with just a semicolon. no extra whitespace!
END;
// Because echo does not behave like a function, the following code is invalid.
($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
?>
Notas
Nota: Este é um construtor de linguagem e não uma função, por isso não é possível chamá-lo através de funções variáveis
add a note
User Contributed Notes 3 notes
pemapmodder1970 at gmail dot com ¶
1 year ago
Jamie Robinson ¶
1 year ago
The {} syntax is useful for printing non array variables as well, an example to illustrate:
<?php
$foo = "foobar";
$bar = "barbaz";
//Will produce the error: Undefined variable: $foo_
echo "$foo_$bar";
//Will print the intended string: "foobar_barbaz"
echo "{$foo}_$bar";
?>
Could even be worth getting into the habit of enclosing all variables in {} when writing echo strings, to be on the safe side.
214363570 at qq dot com ¶
1 year ago
Dear:
Is there a offical function like echoln(), such as
function echoln($s=""){
echo $s."\n";
}
$str = "i love php";
echoln($str);
echoln($str);
echoln($str);
echoln($str);
not is:
echo $str."\n";
echo $str."\n";
echo $str."\n";
echo $str."\n";
echo $str."\n";
Thank you.
Best regards.
