PHP学习系列（1）字符串处理函数（3），php函数

<?<span>php
</span><span>$str</span> = <span>crc32</span>("Hello world!"<span>);
</span><span>echo</span> 'Without %u: '.<span>$str</span>."<br />"<span>;
</span><span>echo</span> 'With %u: '<span>;
</span><span>printf</span>("%u",<span>$str</span><span>);
</span>?>

Without %u: 461707669
With %u: 461707669

<?<span>php
</span><span>$str</span> = <span>crc32</span>("Hello world."<span>);
</span><span>echo</span> 'Without %u: '.<span>$str</span>."<br />"<span>;
</span><span>echo</span> 'With %u: '<span>;
</span><span>printf</span>("%u",<span>$str</span><span>);
</span>?>

Without %u: -1959132156
With %u: 2335835140

<?<span>php
</span><span>if</span> (CRYPT_STD_DES == 1<span>)
{
</span><span>echo</span> "Standard DES: ".<span>crypt</span>("hello world")."\n<br />"<span>;
}
</span><span>else</span><span>
{
</span><span>echo</span> "Standard DES not supported.\n<br />"<span>;
}

</span><span>if</span> (CRYPT_EXT_DES == 1<span>)
{
</span><span>echo</span> "Extended DES: ".<span>crypt</span>("hello world")."\n<br />"<span>;
}
</span><span>else</span><span>
{
</span><span>echo</span> "Extended DES not supported.\n<br />"<span>;
}

</span><span>if</span> (CRYPT_MD5 == 1<span>)
{
</span><span>echo</span> "MD5: ".<span>crypt</span>("hello world")."\n<br />"<span>;
}
</span><span>else</span><span>
{
</span><span>echo</span> "MD5 not supported.\n<br />"<span>;
}

</span><span>if</span> (CRYPT_BLOWFISH == 1<span>)
{
</span><span>echo</span> "Blowfish: ".<span>crypt</span>("hello world"<span>);
}
</span><span>else</span><span>
{
</span><span>echo</span> "Blowfish DES not supported."<span>;
}
?></span>

Standard DES: $1$r35.Y52.$iyiFuvM.zFGsscpU0aZ4e. 
Extended DES not supported. 
MD5: $1$BN1.0I2.$8oBI/4mufxK6Tq89M12mk/ 
Blowfish DES not supported.

13、explode() 函数把字符串分割为数组。

语法：explode(separator,string,limit)

说明：本函数返回由字符串组成的数组，其中的每个元素都是由 separator 作为边界点分割出来的子字符串。

separator 参数不能是空字符串。如果 separator 为空字符串（""），explode() 将返回 FALSE。

如果 separator 所包含的值在string 中找不到，那么 explode() 将返回包含 string 中单个元素的数组。如果设置了 limit 参数，

则返回的数组包含最多 limit 个元素，而最后那个元素将包含 string 的剩余部分。如果 limit 参数是负数，则返回除了最后的 -limit 个元素外的所有元素。

此特性是 PHP 5.1.0 中新增的。

注意：参数 limit 是在 PHP 4.0.1 中加入的。由于历史原因，虽然 implode() 可以接收两种参数顺序，但是 explode() 不行。

你必须保证 <em>separator</em> 参数在 <em>string</em> 参数之前才行。

<?<span>php
</span><span>$str</span> = "Hello world. It's a beautiful day."<span>;
</span><span>print_r</span> (<span>explode</span>(" ",<span>$str</span><span>));
</span>?>

Array
(
[0] => Hello
[1] => world.
[2] => It's
[3] => a
[4] => beautiful
[5] => day.
)

14、fprintf() 函数把格式化的字符串写到指定的输出流（例如：文件或数据库）。

fprintf(stream,format,arg1,arg2,arg++)

<?php
$str = "Hello";
$number = 123;
$file = fopen("test.txt","w");
echo <code>fprintf($file,"%s world. Day number %u",$str,$number)</code>;
?>

27

Hello world. Day number 123

<?php
$number = 123;
$file = fopen("test.txt","w");
<code>fprintf($file,"%f",$number);</code>
?>

123.000000

<?php
$number = 123;
$file = fopen("test.txt","w");
<code>fprintf($file,"With 2 decimals: %1\$.2f\nWith no decimals: %1\$u",$number)</code>;
?>

With 2 decimals: 123.00
With no decimals: 123

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