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.
One or more string expressions to output, separated by commas.
Non-string values will be coerced to strings, even when
the
strict_types directive is enabled.
// 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 $some_var ? 'true': 'false'; // evaluating the expression first and passing it to echo ?>
Surrounding a single argument to echo with parentheses will not
raise a syntax error, and produces syntax which looks like a normal
function call. However, this can be misleading, because the parentheses are actually
part of the expression being output, not part of the echo
syntax itself.
<?php echo "hello"; // outputs "hello"
echo("hello"); // also outputs "hello", because ("hello") is a valid expression
echo(1 + 2) * 3; // outputs "9"; the parentheses cause 1+2 to be evaluated first, then 3*3 // the echo statement sees the whole expression as one argument
echo "hello", " world"; // outputs "hello world"
echo("hello"), (" world"); // outputs "hello world"; the parentheses are part of each expression
echo("hello", " world"); // Throws a Parse Error because ("hello", " world") is not a valid expression ?>
Tip
Passing multiple arguments to echo can avoid
complications arising from the precedence of the concatenation operator in
PHP. For instance, the concatenation operator has higher precedence than
the ternary operator, and prior to PHP 8.0.0 had the same precedence as addition
and subtraction:
<?php // Below, the expression 'Hello ' . isset($name) is evaluated first, // and is always true, so the argument to echo is always $name echo 'Hello ' . isset($name) ? $name : 'John Doe' . '!';
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.
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).
