PHP: Строковые операторы - Manual

downloads | documentation | faq | getting help | mailing lists | reporting bugs | php.net sites | links | conferences | my php.net

search for in the

Операторы, работающие с массивами Логические операторы

Last updated: Sat, 27 Jan 2007

view this page in

# Строковые операторы

В PHP есть два оператора для работы со строками. Первый - оператор конкатенации ('.'), который возвращает объединение левого и правого аргумента. Второй - оператор присвоения с конкатенацией, который присоединяет правый аргумент к левому. Для получения более полной информации ознакомтесь с разделом Оператор присвоения.

`<?php
$a = "Hello ";
$b = $a . "World!"; // $b содержит строку "Hello World!"
$a = "Hello ";
$a .= "World!"; // $a содержит строку "Hello World!"
?>`

Также ознакомьтесь с разделами документации Строки и Функции для работы со строками.

add a note User Contributed Notes
Строковые операторы
kevin at metalaxe dot com
09-Nov-2006 06:57
`I ran the follow script and found that using "$var" was 'mostly' slower than using ' '.$var
<?php
$var = 1;
for( $x=0; $x < 101; $x++ )
{
echo '<br /><br />var = int( '.$var.' )<br />';
$timer->reset();
for( $i=0; $i<100001; $i++ )
{
$string = " {$var} {$var} {$var} {$var} {$var} {$var} {$var} {$var} {$var} {$var} {$var} {$var} {$var} {$var} {$var}";
unset( $string );
}
echo 'One string with 15 $vars was set using one concat 100000 times and took '.$timer->fetch_time().' seconds to execute <br />';
$timer->reset();
for( $i=0; $i<100001; $i++ )
{
$string = ' '.$var.' '.$var.' '.$var.' '.$var.' '.$var.' '.$var.' '.$var.' '.$var.' '.$var.' '.$var.' '.$var.' '.$var.' '.$var.' '.$var.' '.$var;
unset( $string );
}
echo 'One string with 15 instances of $var was set using multiple concats 100000 times and took '.$timer->fetch_time().' seconds to execute';
}
exit();
?>
Replacing $timer with a generic timing class of course.`
caliban at darklock dot com
29-Mar-2006 11:10
`WRT Stephen's note:
My example of concatenation and array methods of string building does not include the interstitial logic, which is expected to include conditionals.
Concatenation method:
$str="This is my list";
if($list=="o") $str.="<ol>";
else $str.="<ul>";
foreach($item as $i) $str.="<li>$i</li>";
if($list=="o") $str.="</ol>";
else $str.="</ul>";
Array method:
$str=array("This is my list");
if($list=="o") $str[]="<ol>";
else $str[]="<ul>";
foreach($item as $i) $str[]="<li>$i</li>";
if($list=="o") $str[]="</ol>";
else $str[]="</ul>";
$str=implode("",$str);
You can't do either of these with a single double-quoted string. However, if what you are doing CAN be done in a single double-quoted string, Stephen is completely correct in observing that you should do that instead of concatenating.`
Stephen Clay
23-Dec-2005 07:10
`<?php
"{$str1}{$str2}{$str3}"; // one concat = fast
$str1. $str2. $str3; // two concats = slow
?>
Use double quotes to concat more than two strings instead of multiple '.' operators. PHP is forced to re-concatenate with every '.' operator.`
caliban at darklock dot com
15-Dec-2004 07:57
`String concatenation is faster than the array method:
$str="";
$str.="Some string";
$str.="Some other string";
...
$str.="The last string";
That runs roughly twice as fast as:
$str=array();
$str[]="Some string";
$str[]="Some other string";
...
$str[]="The last string";
$str=implode("",$str);
Not that I think this is a terribly widespread practice, but I've got an awful lot of legacy code with this array method in it and a comment to the effect that it's faster than string concatenation. Testing has shown the exact opposite, so I figured I'd enlighten anyone else with this misconception.`
anders dot benke at telia dot com
27-Apr-2004 09:53
`A word of caution - the dot operator has the same precedence as + and -, which can yield unexpected results.
Example:
<php
$var = 3;
echo "Result: " . $var + 3;
?>
The above will print out "3" instead of "Result: 6", since first the string "Result3" is created and this is then added to 3 yielding 3, non-empty non-numeric strings being converted to 0.
To print "Result: 6", use parantheses to alter precedence:
<php
$var = 3;
echo "Result: " . ($var + 3);
?>`
php dot net at rinner dot at
19-Feb-2001 05:00
`Also see http://www.php.net/manual/en/language.types.string.php for usage of here doc syntax ("<<<")`
add a note
Операторы, работающие с массивами Логические операторы

Last updated: Sat, 27 Jan 2007
show source | credits | stats | sitemap | contact | advertising | mirror sites
Copyright © 2001-2007 The PHP Group
All rights reserved.
This mirror generously provided by: Yahoo! Inc.
Last updated: Sat Mar 10 09:32:46 2007 PST