>PHP: echo - Manual

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

Muestra todos sus parÃ¡metros por la salida definida.

echo() no es realmente una funciÃ³n (es una sentencia del lenguaje) de modo que no se requiere el uso de los parÃ©ntesis. De hecho, si se indica mÃ¡s de un parÃ¡metro, no se pueden incluir los parÃ©ntesis.
Ejemplo 1. Ejemplos de echo()

<?php echo "Hola Mundo"; echo "Este texto se extiende por varias lineas. Los saltos de linea tambien se envian"; echo "Este texto se extiende\npor varias lineas. Los saltos de linea\ntambien se envian."; echo "Para escapar caracteres, se debe indicar \"de esta forma\"."; // Se pueden usar variables dentro de una sentencia echo $saludo = "que tal"; $despedida = "hasta luego"; echo "hola, $saludo"; // hola, que tal // Tambien se pueden usar arrays $cadena = array("valor" => "saludo desde un array"); echo "Esto es un {$cadena['valor']} "; // Esto es un saludo desde un array // Si se emplean comillas simples, se muestra el nombre de la variable, no su valor echo 'hola, $saludo'; // hola, $saludo // Si no se anade ningun caracter, tambien es posible emplear echo para mostrar el valor de las variables echo $saludo; // que tal echo $saludo,$despedida; // que talhasta luego // El uso de echo con multiples parametros es igual que realizar una concatenacion echo 'Esta ', 'cadena ', 'esta ', 'construida ', 'con muchos parametros.', chr(10); echo 'Esta ' . 'cadena ' . 'esta ' . 'construida ' . 'empleando concatenacion.' . "\n"; echo <<<FIN Este texto utiliza una sintaxis especial que permite mostrar varias lineas de texto. La etiqueta que indica el final del bloque de texto (y que en este caso es "FIN") debe aparecer en una linea que contenga solamente el valor de la etiqueta y un caracter de punto y coma (ni siquiera puede contener espacios en blanco). FIN; // Como echo no es una funcion, el siguiente codigo no es valido ($una_variable) ? echo 'verdadero' : echo 'falso'; // Sin embargo, los siguientes ejemplos si que funcionan. ($una_variable) ? print('verdadero'): print('falso'); // print es una funcion echo $una_variable ? 'verdadero': 'false'; // se modifica la sentencia a mostrar en funcion del valor de $una_variable ?>

echo() tambiÃ© funciona con una sintaxis abreviada formada por una etiqueta de apertura seguida de un signo igual. La sintaxis abreviada solamente funciona si se encuentra habilitada la directiva de configuraciÃ³n short_open_tag.


Tengo <?=$numero?> unidades.

En el siguiente articulo de la "FAQTs Knowledge Base" http://www.faqts.com/knowledge_base/view.phtml/aid/1/fid/40 puede encontrarse una argumentaciÃ³n sobre las diferencias entre las funciones print() y echo().

Nota: Puesto que esto es una construcciÃ³n del lenguaje y no una funciÃ³n, no puede ser llamado usando funciones variables

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

add a note User Contributed Notes
echo

rwruck
27-Jan-2006 01:15


It should be mentioned here that the script will be aborted if you output something in response to a HTTP HEAD request.

In the following example, the second line will NOT be written to the file. Any registered shutdown function will be called, though:



<?php

$hf = fopen('head.log', 'ab');

fwrite($hf, "before output\n");

echo "Test";

fwrite($hf, "after output\n");

fclose($hf);

?>



This is normal behaviour; see the description of $_SERVER.

lorenpr at gmail dot com
14-Sep-2005 09:12


I hope this ternary thing isn't overkill. Last thing - I would just like to make you aware of the side effect when you do this statement, 

 

echo $some_var ? print 'true': print 'false';



The result would be either 'true1' or 'false1', depending on whether $some_var is true or false respectively. This happens because of what I mentioned earlier. Figure it out.

lorenpr at gmail dot com
14-Sep-2005 08:58


linus is correct.

The ternary relationship is evaluated first, then echo prints the result.



Also, keep in mind

(condition? a : b) 

reads 

if(condition) return a; else return b;



So what makes 

A. echo ($somevar) ? 'true' : 'false';



different from



B. ($somevar) ? echo 'true' : echo 'false';



is the ternary relationship in A reads

if (condition) return 'true'; else return 'false';



while in B it reads

if(condition) return (echo 'true'); else return (echo 'false');



- an invalid statement, since echo evaluates to void.

linus.martensson a gmail
24-Aug-2005 02:03


Simple. it reads like echo (($somevar)?'true';'false'); and outputs the result, unless I'm mistaken.

shannonmoeller at gmail dot com
09-Aug-2005 04:31


In reply to lorenpr at gmail dot com:



If what you say is true, why does this work?



<?php

echo ($somevar) ? 'true' : 'false'; //works

?>

lorenpr at gmail dot com
28-Jul-2005 10:17


I just want to point out something to beginners. The documentation is misleading where it says:



// Because echo is not a function, following code is invalid.

($some_var) ? echo 'true' : echo 'false';



The code is invalid, but not because 'echo' is a language construct, but rather because 'echo' does not return a value. 

So don't be mislead: the syntax used above is certainly not limited to functions.



You must keep in mind that the job of the ternary syntax used is not actually to display anything, but to test a boolean relationship. The 'print' statement would work because it always returns a 1, which in php, is interpreted to a boolean  'true'. Things that return 'void' cannot be expected to evaluate to a 'true' or 'false', and that is why using 'echo' in this particular case is invalid.

Jason Carlson - SiteSanity
16-May-2005 10:28


In response to Ryan's post with his echobig() function, using str_split wastes memory resources for what you are doing. 



If all you want to do is echo smaller chunks of a large string, I found the following code to perform better and it will work in PHP versions 3+



<?php

function echobig($string, $bufferSize = 8192)

{

  // suggest doing a test for Integer & positive bufferSize

  for ($chars=strlen($string)-1,$start=0;$start <= $chars;$start += $bufferSize) {

    echo substr($string,$start,$buffer_size);

  }

}

?>

renrutal at gmail dot com
28-Mar-2005 03:34


Note that:



<?php

echo "2 + 2 = " . 2+2; // This will print 4

echo "2 + 2 = " , 2+2; // This will print 2+2 = 4

?>



The commas will parse the result of the expressions correctly.

ryan at wonko dot com
27-Feb-2005 12:56


Due to the way TCP/IP packets are buffered, using echo to send large strings to the client may cause a severe performance hit. Sometimes it can add as much as an entire second to the processing time of the script. This even happens when output buffering is used.



If you need to echo a large string, break it into smaller chunks first and then echo each chunk. The following function will do the trick in PHP5:



<?php

function echobig($string, $bufferSize = 8192)

{

    $splitString = str_split($string, $bufferSize);



    foreach($splitString as $chunk)

        echo $chunk;

}

?>

Truffy
15-Jan-2005 01:02


You can use braces around variables as well as array items. This is useful to help recognition of your variables in your code, but most useful where the variable iteslf cannot be separated with spaces from the preceding/following code, for exmple in a file path:



If a path is assigned the variable $path, then this code will not work:



echo "$pathhttp://indices.com.es/index.html";



whereas this will



echo "{$path}http://indices.com.es/index.html";

zombie)at(localm)dot(org)
25-Jan-2003 11:26


[Ed. Note: During normal execution, the buffer (where echo's arguments go) is not flushed (sent) after each write to the buffer. To do that you'd need to use the flush() function, and even that may not cause the data to be sent, depending on your web server.]





Echo is an i/o process and i/o processes are typically time consuming. For the longest time i have been outputting content by echoing as i get the data to output. Therefore i might have hundreds of echoes in my document. Recently, i have switched to concatenating all my string output together and then just doing one echo at the end. This organizes the code more, and i do believe cuts down on a bit of time. Likewise, i benchmark all my pages and echo seems to influence this as well. At the top of the page i get the micro time, and at the end i figure out how long the page took to process. With the old method of "echo as you go" the processing time seemed to be dependent on the user's net connection as well as the servers processing speed. This was probably due to how echo works and the sending of packets of info back and forth to the user. One an one script i was getting .0004 secs on a cable modem, and a friend of mine in on dialup was getting .2 secs. Finally, to test that echo is slow; I built strings of XML and XSLT and used the PHP sablotron functions to do a transformation and return a new string. I then echoed the string. Before the echo, the process time was around .025 seconds and .4 after the echo. So if you are big into getting the actual processing time of your scripts, don't include echoes since they seem to be user dependent. Note that this is just my experience and it could be a fluke.

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