to handle result of mb_strpos function in php: php, mb

to handle result of mb_strpos function in php

We are validating input characters in our php pages. Following is the code we have written to accomplish this. Since our input boxes should accept special characters like ÀÁetc., we have used mb_strpos function. But the problem is, if the function could not find a string's position (this meant, the character is invalid), it returns empty string. The application is treating the empty string as "0"(zero) and allows invalid character.

Experts, Kindly guide us whether we are doing the correct coding to accomplish our desired task.

Thanks,
eprm.

$StringValue = "abcdefghijklmnopqrstuvwxyz0123456789_-.@ABCDEFGHIJKLMNOPQRSTUVWXYZÀÁÂÃÄÅÆÇÈÉÊËÌÍÎÏÐÑÒÓÔÕÖ×ØÙÚÛÜÝÞßàáâãäåæçèéêëìíîïðñòóôõö÷øùúûüýþÿ()'&/ ";
$value = $_POST["txtName"];
for($i=0; $i < strlen(utf8_decode($value)); $i++)
{
 $char_pos=0;
 $char_sub=mb_substr($value, $i, 1,'UTF-8');
 $char_pos=mb_strpos($StringValue, $char_sub, 0,'UTF-8');
 if(($char_pos) >= 0)
 {
  echo 'VALID Char';
 }
 else
 {
  echo 'Invalid Characters found';
 }
}

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<?php // RAY_temp_not_utf8.php error_reporting(E_ALL); echo "<pre>\n"; // TEST DATA FROM THE ORIGINAL POST $StringValue = "abcdefghijklmnopqrstuvwxyz0123456789_-.@ABCDEFGHIJKLMNOPQRSTUVWXYZÀÁÂÃÄÅÆÇÈÉÊËÌÍÎÏÐÑÒÓÔÕÖ×ØÙÚÛÜÝÞßàáâãäåæçèéêëìíîïðñòóôõö÷øùúûüýþÿ()'&/ "; $old = $StringValue; $new = ''; // LOOK A THE BYTES ONE AT A TIME (IMPOSSIBLE WITH UTF-8) while(strlen($old)) { // PICK A CHARACTER $i = substr($old,0,1); $old = substr($old,1); // SHOW THE CHARACTER, AND SAVE BACKWARDS IN A NEW VARIABLE echo "\n$i"; $new = $i . $new; } echo "\n\n"; // REVERSE THE NEW STRING $new = strrev($new); // INSPECT THE STRINGS var_dump($StringValue); var_dump($new); if ($StringValue === $new) echo "\nEQUAL";

Can you please post the code example that shows the substr function failing to find the correct position of the characters? I'm wondering if there is something else amiss. See the code snippet - it works perfectly for me.

Thanks, ~Ray

<?php // RAY_temp_not_utf8.php
error_reporting(E_ALL);
echo "<pre>\n";  
// TEST DATA FROM THE ORIGINAL POST
$StringValue = "abcdefghijklmnopqrstuvwxyz0123456789_-.@ABCDEFGHIJKLMNOPQRSTUVWXYZÀÁÂÃÄÅÆÇÈÉÊËÌÍÎÏÐÑÒÓÔÕÖ×ØÙÚÛÜÝÞßàáâãäåæçèéêëìíîïðñòóôõö÷øùúûüýþÿ()'&/ ";  
$old = $StringValue;
$new = '';  
// LOOK A THE BYTES ONE AT A TIME (IMPOSSIBLE WITH UTF-8)
while(strlen($old))
{
    // PICK A CHARACTER
    $i = substr($old,0,1);
    $old = substr($old,1); 
    // SHOW THE CHARACTER, AND SAVE BACKWARDS IN A NEW VARIABLE
    echo "\n$i";
    $new = $i . $new;
}
echo "\n\n";  
// REVERSE THE NEW STRING
$new = strrev($new);  
// INSPECT THE STRINGS
var_dump($StringValue);
var_dump($new);
if ($StringValue === $new) echo "\nEQUAL"; 

// DETERMINE THE POSITION OF EACH CHARACTER BY USING PHP strpos() AND substr() FUNCTIONS
$old = $StringValue; 
while(strlen($old))
{
    // PICK A CHARACTER
    $i = substr($old,0,1);
    $old = substr($old,1); 
    // SHOW THE CHARACTER
    echo "\n$i";
    
    // MAN PAGE: http://us3.php.net/manual/en/function.strpos.php
    $poz = strpos($StringValue, $i);
    echo " strpos=$poz";
    
    // MAN PAGE: http://us3.php.net/manual/en/function.substr.php
    $sub = substr($StringValue, $poz, 3);
    echo " substr=$sub";
}
echo "\n\n";

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<?php // RAY_temp_regex_not_utf8.php error_reporting(E_ALL); echo "<pre>\n"; // A REGEX TO DISALLOW CHARACTERS NOT IN THE TEST DATA $regex = "/[^abcdefghijklmnopqrstuvwxyz0123456789_\-\.@ABCDEFGHIJKLMNOPQRSTUVWXYZÀÁÂÃÄÅÆÇÈÉÊËÌÍÎÏÐÑÒÓÔÕÖ×ØÙÚÛÜÝÞßàáâãäåæçèéêëìíîïðñòóôõö÷øùúûüýþÿ()'&\/ ]/"; // TEST DATA FROM THE ORIGINAL POST $StringValue = "abcdefghijklmnopqrstuvwxyz0123456789_-.@ABCDEFGHIJKLMNOPQRSTUVWXYZÀÁÂÃÄÅÆÇÈÉÊËÌÍÎÏÐÑÒÓÔÕÖ×ØÙÚÛÜÝÞßàáâãäåæçèéêëìíîïðñòóôõö÷øùúûüýþÿ()'&/ "; // ADDING SOME INVALID CHARACTER TO THE END OF THE TEST DATA $old = $StringValue; $old .= '?#*'; // LOOK A THE BYTES ONE AT A TIME (IMPOSSIBLE WITH UTF-8) while(strlen($old)) { // PICK A CHARACTER $i = substr($old,0,1); $old = substr($old,1); echo "\n$i"; // TEST THE CHARACTER - IF IT MATCHES, IT IS NOT VALID if (preg_match($regex, $i)) echo " INVALID"; } echo "\n\n"; // ADDING SOME INVALID CHARACTER TO THE END OF THE TEST DATA $old = $StringValue; $old .= '?#*'; // LOOK A THE BYTES THREE AT A TIME while(strlen($old)) { // PICK A CHARACTER $i = substr($old,0,3); $old = substr($old,1); echo "\n$i"; // TEST THE CHARACTER STRING - ON MATCH, IT IS NOT VALID if (preg_match($regex, $i)) echo " INVALID"; } echo "\n\n";

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to handle result of mb_strpos function in php

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php

mb_strpos

string position

PHP Scripting Language

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