PHP replaces part of the content with asterisks_PHP tutorial-PHP Tutorial-php.cn

PHP replaces part of the content with asterisks

In a recent project, I encountered the need to hide the middle digits of someone's mobile phone number and only display the last 4 digits of the ID number. At the beginning, I searched online and saw that someone used the substr_replace function to replace it. I also used this function later, but it was not very useful when I used it.

1. substr_replace

Let’s take a look at the syntax of this function:

substr_replace(string,replacement,start,length)

Parameters Description

string Required. Specifies the string to check.

replacement Required. Specifies the string to be inserted.

start

Required. Specifies where in the string to begin replacement.

Positive number - start replacing

at the start offset

Negative numbers - replace

starting at the start offset from the end of the string

0 - Start replacing

at the first character in the string

charlist

Optional. Specifies how many characters to replace.

Positive number - the length of the string to be replaced

Negative number - the number of characters to be replaced starting from the end of the string

0 - insert instead of replace

1. When start and charlist are both positive numbers, it is very easy to understand and symbolizes human logic. Start starts from 0, as shown below. According to the conditions, the green element will be the element to be replaced

2. When start is a negative number and charlist is a positive number, it is easy to understand

3. When start is a positive number and charlist is a negative number, I misunderstood this at first

4. When start is a negative number and charlist is a negative number, one thing to note is: if start is a negative number and length is less than or equal to start, then length is 0. This trap is quite easy to step into

5. When charlist is 0, it becomes insertion instead of replacement, eh. . .

After using it, I feel that it is not very smooth. Although it can meet my current needs, if I need some expansion in the future, it will be quite difficult to use, so I thought of constructing one myself, which will be convenient to use in the future. .

2. Homemade asterisk replacement function

replaceStar($str, $start, $length = 0)

Parameters Description

str Required. Specifies the string to check.

start

Required. Specifies where in the string to begin replacement.

Positive number - start replacing

at the start offset

Negative numbers - replace

starting at the start offset from the end of the string

0 - Start replacing

at the first character in the string

length

Optional. Specifies how many characters to replace.

Positive number - the length of the string to be replaced, from left to right

Negative number - the length of the string to be replaced, from right to left

0 - If start is a positive number, start from start and go left to the end

　 - If start is a negative number, start from start and go to the right to the end

The first two parameters are the same as above, and the last parameter is different from above

1. When start and length are both positive numbers, it behaves the same as substr_replace

2. When start is a negative number and length is a positive number, it behaves the same as substr_replace

substr_replace

replaceStar

start is a positive number and length is a negative number

start is a negative number and length is a negative number

start is a positive number and the length is 0 Perform insertion operation

start is a negative number and the length is 0 Perform insertion operation

3. Source code sharing

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public static function replaceStar($str, $start, $length = 0)

{

$i = 0;

$star = '';

if($start >= 0) {

if($length > 0) {

$str_len = strlen($str);

$count = $length;

if ($ Start & GT; = $ Str_len) {// When the starting bid is greater than the length of the string, it will not replace it

$count = 0;

}

}elseif($length < 0){

$str_len = strlen($str);

$count = abs($length);

$start = $str_len - 1;

}

$offset = $start - $count + 1;//Subtract the quantity from the starting point subscript and calculate the offset

Use the length from the starting point to the far left

}else {

$str_len = strlen($str);

$count = $str_len - $start;//Calculate the quantity to be replaced

}

}else {

if($length > 0) {

$offset = abs($start);

$count = $offset >= $length ? $length : $offset;//When greater than or equal to the length, it does not exceed the rightmost

}elseif($length < 0){

$str_len = strlen($str);

$end = $str_len + $start;//Calculate the end value of the offset

$offset = abs($start + $length) - 1;//Calculate the offset, since they are all negative numbers, add them up

$start = $str_len - $offset;//Calculate the starting value

$start = $start >= 0 ? $start : 0;

$count = $end - $start + 1;

}else {

$str_len = strlen($str);

$count = $str_len + $start + 1;//Calculate the length of offset required

$start = 0;

}

while ($i < $count) {

$star .= '*';

$i++;

}

return substr_replace($str, $star, $start, $count);

}

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I am not good at algorithms, so I will use very common logic to show it here, without using any mathematical formulas.

1. if($start >= 0) here is the branch where start is greater than or equal to 0 and less than 0

2. Among the start points, make three branches with length greater than 0, less than 0 and equal to 0 respectively

3. Finally calculate start, count and the asterisk string to be replaced. The finally calculated start and count are both positive numbers. Use substr_replace to replace them

4. Unit Test

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public function testReplaceStar()

{

$actual = App_Util_String::replaceStar('123456789', 3, 2);

$this->assertEquals($actual, '123**6789');

$actual = App_Util_String::replaceStar('123456789', 9);

$this->assertEquals($actual, '123456789');

$actual = App_Util_String::replaceStar('123456789', 9, 2);

$this->assertEquals($actual, '123456789');

$actual = App_Util_String::replaceStar('123456789', 9, -9);

$this->assertEquals($actual, '************');

$actual = App_Util_String::replaceStar('123456789', 9, -10);

$this->assertEquals($actual, '************');

$actual = App_Util_String::replaceStar('123456789', 9, -11);

$this->assertEquals($actual, '************');

$actual = App_Util_String::replaceStar('123456789', 3);

$this->assertEquals($actual, '123******');

$actual = App_Util_String::replaceStar('123456789', 0);

$this->assertEquals($actual, '************');

$actual = App_Util_String::replaceStar('123456789', 0, 2);

$this->assertEquals($actual, '**3456789');

$actual = App_Util_String::replaceStar('123456789', 3, -3);

$this->assertEquals($actual, '1***56789');

$actual = App_Util_String::replaceStar('123456789', 1, -5);

$this->assertEquals($actual, '**3456789');

$actual = App_Util_String::replaceStar('123456789', 3, -3);

$this->assertEquals($actual, '1***56789');

$actual = App_Util_String::replaceStar('123456789', -3, 2);

$this->assertEquals($actual, '123456**9');

$actual = App_Util_String::replaceStar('123456789', -3, 5);

$this->assertEquals($actual, '123456***');

$actual = App_Util_String::replaceStar('123456789', -1, 2);

$this->assertEquals($actual, '12345678*');

$actual = App_Util_String::replaceStar('123456789', -1, -2);

$this->assertEquals($actual, '1234567**');

$actual = App_Util_String::replaceStar('123456789', -4, -7);

$this->assertEquals($actual, '******789');

$actual = App_Util_String::replaceStar('123456789', -1, -3);

$this->assertEquals($actual, '123456***');

$actual = App_Util_String::replaceStar('123456789', -1);

$this->assertEquals($actual, '*********');

$actual = App_Util_String::replaceStar('123456789', -2);

$this->assertEquals($actual, '********9');

$actual = App_Util_String::replaceStar('123456789', -9);

$this->assertEquals($actual, '*23456789');

$actual = App_Util_String::replaceStar('123456789', -10);

$this->assertEquals($actual, '123456789');

$actual = App_Util_String::replaceStar('123456789', -10, -2);

$this->assertEquals($actual, '123456789');

}