php-doc-en/reference/strings/functions/echo.xml

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  <refentry id="function.echo">
   <refnamediv>
    <refname>echo</refname>
    <refpurpose>Output one or more strings</refpurpose>
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>void</type><methodname>echo</methodname>
      <methodparam><type>string</type><parameter>arg1</parameter></methodparam>
      <methodparam choice="opt"><type>string</type><parameter>...</parameter></methodparam>
     </methodsynopsis>
    <simpara>
     Outputs all parameters.
    </simpara>
    <para>
     <function>echo</function> is not actually a function (it is a
     language construct), so you are not required to use parentheses
     with it. <function>echo</function> (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 <function>echo</function>, the parameters
     must not be enclosed within parentheses.
    </para>
    <para>
     <example>
      <title><function>echo</function> examples</title>
      <programlisting role="php">
<![CDATA[
<?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 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 $some_var ? 'true': 'false'; // changing the statement around
?>
]]>
      </programlisting>
     </example>
    </para>
    <para>
     <function>echo</function> also has a shortcut syntax, where you can
     immediately follow the opening tag with an equals sign. This short syntax
     only works with the <link
     linkend="ini.short-open-tag">short_open_tag</link> configuration setting
     enabled.
     <informalexample>
      <programlisting role="php">
<![CDATA[
I have <?=$foo?> foo.
]]>
      </programlisting>
     </informalexample>
    </para>
    <simpara>
     For a short discussion about the differences between 
     <function>print</function> and <function>echo</function>, see this FAQTs
     Knowledge Base Article: <ulink url="&url.echo-print;">&url.echo-print;
     </ulink>
    </simpara>
    
    &note.language-construct;
    
    <simpara>
     See also
     <function>print</function>,
     <function>printf</function>, and
     <function>flush</function>.
    </simpara>
   </refsect1>
  </refentry>

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