PHP, Structures and Functions, STRINGS

If $offset < 0 the counting starts from the end of the STRING.

The default $length value is the largest of the length of the $str compared to the length of $main_str minus $offset.

This function returns a NEGATIVE value if $main_str from position $offset is LESS than $str length.

This function returns a POSITIVE value if $main_str from position $offset is GREATER than $str length.

If $offset is EQUAL to, (prior to PHP 7.2.18, 7.3.5), or GREATER than the length of $main_str, or the $length is set and is less than 0, (or, prior to PHP 5.5.11, less than 1) this function prints a WARNING and returns FALSE.

This function is binary-safe

In PHP, some functions are marked as binary-safe, it means that the functions works correctly even when you pass binary data.


<?php

int substr_compare ( str $main_str , 
                                 str $str , 
                                 int $offset [, 
                                 int $length [, 
                                bool $case_insensitivity = FALSE ]] ) 


where,

$main_str = The main STRING being compared

$str = The secondary STRING being compared

$offset = The offset where to start counting

$length = The length of the comparisson

$case_insensitivity = To control the comparisson case
                                ( SEE the TABLE )
?>

$main_str

The main STRING being compared.

$str

The secondary STRING being compared.

$offset

The $offset where to start counting.

$length

The $length where to start the comparisson.

$case_insensitivity

VALUE	MEANING
FALSE	The comparisson will be case sensitive.
TRUE	The comparisson will be case insensitive.
ed48

EXERCISE


<table width="100%" cellspacing="5" 
cellpadding="5" border="1">
<tbody><tr>
<td width="12%">$offset</td>
<td width="9%">RETURNS</td>
<td width="56%">SECTION of $main_str 
from $offset to $length</td>
<td width="23%">$str</td>
</tr>
<?php

$main_str01 = "NOT CONSTITUTIONAL";
$str01 = "CONSTITUTIONAL";
// UPPERCASE

for ($offset01 = 0; 
      $offset01 <= strlen($main_str01) - 1;
      $offset01++)
{
$comp01 = substr_compare($main_str01, $str01, $offset01); 
// Without consider the length of $str01 

echo '<tr><td>' . $offset01 . '</td><td>' . $comp01 . 
'</td><td>' . substr($main_str01, $offset01) . 
'</td><td>' . $str01 . '</td></tr>';
}

?>
<tr><td colspan="4">ed48</td></tr></tbody></table>

EXERCISE


<table width="100%" cellspacing="5" 
cellpadding="5" border="1">
<tbody><tr>
<td width="12%">$offset</td>
<td width="9%">RETURNS</td>
<td width="56%">SECTION of $main_str 
from $offset to $length</td>
<td width="23%">$str</td>
</tr>
<?php

$main_str02 = "NOT CONSTITUTIONAL";
$str02 = "CONSTITUTIONAL";
// UPPERCASE

for ($offset02 = 0; 
       $offset02 <= strlen($main_str02) - 1; 
       $offset02++)
{
$comp02 = substr_compare($main_str02, $str02, 
                              $offset02, strlen($str02)); 
// Considering the length of $str02

echo '<tr><td>' . $offset02 . '</td><td>' . $comp02 . 
'</td><td>' . substr($main_str02, $offset02) . 
'</td><td>' . $str02 . '</td></tr>';
}

?>
<tr><td colspan="4">ed48</td></tr></tbody></table>

EXERCISE


<table width="100%" cellspacing="5" 
cellpadding="5" border="1">
<tbody><tr>
<td width="12%">$offset</td>
<td width="9%">RETURNS</td>
<td width="56%">SECTION of $main_str 
from $offset to $length</td>
<td width="23%">$str</td>
</tr>
<?php

$main_str03 = "NOT CONSTITUTIONAL";
$str03 = "constitutional";
// lowercase

for ($offset03 = 0; 
        $offset03 <= strlen($main_str03) - 1; 
        $offset03++)
{
$comp03 = substr_compare($main_str03, 
                                    $str03, $offset03); 
// Without consider the length of $str03 

echo '<tr><td>' . $offset03 . '</td><td>' . $comp03 . 
'</td><td>' . substr($main_str03, $offset03) . 
'</td><td>' . $str03 . '</td></tr>';
}

?>
<tr><td colspan="4">ed48</td></tr></tbody></table>

EXERCISE


<table width="100%" cellspacing="5" 
cellpadding="5" border="1">
<tbody><tr>
<td width="12%">$offset</td>
<td width="9%">RETURNS</td>
<td width="56%">SECTION of $main_str 
from $offset to $length</td>
<td width="23%">$str</td>
</tr>
<?php

$main_str04 = "Não é sempre que 
se pode confiar em alguém!";
/* It is not always
you can trust someone! */

// May experience problems 
// in languages other than English

$str04 = "SEMPRE";
// UPPERCASE

for ($offset04 = 0; 
       $offset04 <= strlen($main_str04) - 1; 
       $offset04++)
{
$comp04 = substr_compare($main_str04, 
                                   $str04, $offset04); 
// Without consider the length of $str04 

echo '<tr><td>' . $offset04 . '</td><td>' . $comp04 . 
'</td><td>' . substr($main_str04, $offset04) . 
'</td><td>' . $str04 . '</td></tr>';
}

?>
<tr><td colspan="4">ed48</td></tr></tbody></table>

EXERCISE


<?php

var_dump(substr_compare("abcde", "df", -2) < 0);
echo '<br><br>';
var_dump(substr_compare("abcde", "df", -2, null) < 0);
echo '<br><br>';
var_dump(substr_compare("abcde", "bc", 1, 2));
echo '<br><br>';
var_dump(substr_compare("abcde", "bcg", 1, 2));
echo '<br><br>';
var_dump(substr_compare("abcde", "BC", 1, 2, true));
echo '<br><br>';
var_dump(substr_compare("abcde", "bc", 1, 3) > 0);
echo '<br><br>';
var_dump(substr_compare("abcde", "cd", 1, 2) < 0);
echo '<br><br>';
var_dump(substr_compare("abcde", "abc", 5, 1));
echo '<br><br>';
var_dump(substr_compare("abcde", "abcdef", -10, 10) < 0);
echo '<br><br>';
var_dump(substr_compare("abcde", "abc", 0, 0));
echo "<br><br>Test<br><br><br>";

try {
    substr_compare("abcde", "abc", 0, -1);
} catch (\ValueError $e) {
    echo $e->getMessage() . "<br>";
}
echo '<br><br>';
var_dump(substr_compare("abcde", "abc", -1, NULL, -5) > 0);

?>