WeberTrivia.com -> PHP Manual -> echo

Description

void echo ( string arg1 [, string argn...])

Outputs all parameters.

echo() is not actually a function (it is a language construct) so you are not required to use parentheses with it. In fact, if you want to pass more than one parameter to echo, you must not enclose the parameters within parentheses.

Example 1. echo() examples

 <?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
$bar = array("value" => "foo");

echo "this is {$bar['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 is not a function, following code is invalid. 
($some_var) ? echo 'true' : echo 'false';

// However, the following examples will work:
($some_var) ? print('true'): print('false'); // print is a function
echo $some_var ? 'true': 'false'; // changing the statement around
?>

echo() also has a shortcut syntax, where you can immediately follow the opening tag with an equals sign. This short syntax only works with the short_open_tag configuration setting enabled.

I have <?=$foo?> foo.

For a short discussion about the differences between print() and echo(), see this FAQTs Knowledge Base Article: http://www.faqts.com/knowledge_base/view.phtml/aid/1/fid/40

Note: Because this is a language construct and not a function, it cannot be called using variable functions

See also print(), printf(), and flush().