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Manual: eval
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eval

(unknown)

eval -- 文字列を PHP コードとして評価する

説明

void eval (string code_str)

eval() は、code_str で与えられた文字列を PHP コードとして評価します。 中でも、データベースのテキストフィールドにコードを保存し、 後で実行するためには便利です。

eval() を使用する際、注意するべき点が いくつかあります。 パーサーが eval()の処理中に落ちないように、 渡す文字列はセミコロンで文が終了するといった有効なPHPコード である必要があります。また、code_str の 中の文字を適切にエスケープする必要があります。

eval()の中で値を与えた変数は、 この後、メインスクリプトの中でもこれらの値を維持することも 覚えておいて下さい。

例 1. eval()の例 - 簡単なテキストのマージ 


<?php
$string = 'cup';
$name = 'coffee';
$str = 'This is a $string with my $name in it.<br>';
echo $str;
eval( "\$str = \"$str\";" );
echo $str;
?>

上の例は、以下を表示します。 

This is a $string with my $name in it.
This is a cup with my coffee in it.


User Contributed Notes: eval

qfinger@mlink.net
10-May-1999 11:06
To include HTML in the string passed to eval, precede it with a PHP closing tag. Once you have finished your HTML block, insert a PHP opening tag.

eg.
<PRE>
$str = "?><H1><I>Hello, World!</I></H1>&lt;?"
eval( $str );
</PRE>
It will produce:
<PRE>
<H1><I>Hello, World!</I></H1>
</PRE>

noor@comrax.com
19-Nov-1999 07:34
Regarding eval()'ing a string that contains PHP and HTML code, this can be done easily using the following technique:

&lt;?

$value = 5;
$string = '&lt;?php echo "Hello, world. value = $value"; ?>';

eval( "?>$string" );

?>

Regarding the note mentioned before, the trailing '&lt;?' is not necessary and actually will write '&lt;?' in the evaluated HTML code.

The above code will produce:

Hello, world. value = 5

Have fun!
Noor Dawod, CTO
http://www.comrax.com/



sidi@bash.nl
28-Feb-2000 01:12
Eval has no return value. It can not be used as a function, only as a procedure.



cornholi@x-treme.gr
20-Mar-2000 06:42
ANSWER TO: Rob.Buttrose@flinders.edu.au
Try this , Rob! Just Found it out!
<PRE>
for($i = 1; $i <11; $i++)
eval("\$next = \$item".$i.";");
</PRE>

cleong@organic.com
23-Mar-2000 07:02
For people doing cross version PHP development, use eval() to dynamically define functions that exists in PHP4 but not PHP3. For example:

<PRE>
if(floor(phpversion()) == 3)
{
eval('

function in_array($needle, $haystack)
{
reset($haystack);
while(list($key, $val) = each($haystack))
{
if($val == $needle)
{
return true;
}
}
return false;
}

');
}
</PRE>

You can just add the eval(' ... ') without reformatting your code. Need to replace any \ with \\ however.



andy@harmonyworks.com
17-Apr-2000 05:34
Be very careful using eval with data which comes from the browser! It can create a major security hole in your PHP script.

cornholi@x-treme.gr
19-Jul-2000 02:23
//let's say you have 5 variables

$num_of_vars=5;
for ($i=0; $i < $num_of_vars; $i++)
{
//suppose item1, item2 ... are the variables
eval("\$item_array[]=\$item".($i+1).";");
//item_array has their values
echo $item_array[$i]
}

That was it. what do you think?

 About Notes

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