PHP filter ascii control characters_PHP tutorial

<span>/*</span><span>* 
* 根据ascii码过滤控制字符 
* @param type $string 
</span><span>*/</span>
<span>public</span> <span>static</span> <span>function</span> special_filter(<span>$string</span><span>) 
{ 
</span><span>if</span>(!<span>$string</span>) <span>return</span> ''<span>;

</span><span>$new_string</span> = ''<span>; 
</span><span>for</span>(<span>$i</span> =0; <span>isset</span>(<span>$string</span>[<span>$i</span>]); <span>$i</span>++<span>) 
{ 
</span><span>$asc_code</span> = <span>ord</span>(<span>$string</span>[<span>$i</span>]); <span>//</span><span>得到其asc码</span>
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</span><span>//</span><span>以下代码旨在过滤非法字符 </span>
<span>if</span>(<span>$asc_code</span> == 9 || <span>$asc_code</span> == 10 || <span>$asc_code</span> == 13<span>){ 
</span><span>$new_string</span> .= ' '<span>; 
} 
</span><span>else</span> <span>if</span>(<span>$asc_code</span> > 31 && <span>$asc_code</span> != 127<span>){ 
</span><span>$new_string</span> .= <span>$string</span>[<span>$i</span><span>]; 
} 
}

</span><span>return</span> <span>trim</span>(<span>$new_string</span><span>); 
}</span>