PHP Program - Reverse a given String
In PHP, the reverse of a given string can be found out by using below mentioned methods.
Method 1: Using iteration
In the example below, the string called MyString is reversed using ReverseString() function. Two variables l and r are created which initially points to first and last character of the string. If l is less than r, then the characters of MyString at indices l and r swapped. After swapping, l is increased by one and r is decreased by one until they cross each other. Finally, MyString will contain the reversed value of the initial string.
<?php function ReverseString($MyString) { $l = 0; $r = strlen($MyString) - 1; while($r > $l){ //swapping characters at indices l and r $c = $MyString[$l]; $MyString[$l] = $MyString[$r]; $MyString[$r] = $c; $l++; $r--; } echo "$MyString \n"; } ReverseString("Hello World"); ReverseString("Programming is fun"); ReverseString("Reverse this string"); ?>
The above code will give the following output:
dlroW olleH nuf si gnimmargorP gnirts siht esreveR
Method 2: Using Recursion
The above result can also be achieved using recursive function. Consider the example below:
<?php function ReverseString($MyString) { if(($MyString == null) || (strlen($MyString) <= 1)) { echo ($MyString); } else { echo ($MyString[strlen($MyString) - 1]); ReverseString(substr($MyString, 0, (strlen($MyString) - 1))); } } ReverseString("Hello World"); echo "\n"; ReverseString("Programming is fun"); echo "\n"; ReverseString("Reverse this string"); echo "\n"; ?>
The above code will give the following output:
dlroW olleH nuf si gnimmargorP gnirts siht esreveR
Method 3: Printing the string in reverse order
The same can be achieved by printing the string in reverse order. Consider the example below:
<?php function ReverseString($MyString) { $last = strlen($MyString) - 1; for($i = $last; $i >= 0; $i--) { echo $MyString[$i]; } echo "\n"; } ReverseString("Hello World"); ReverseString("Programming is fun"); ReverseString("Reverse this string"); ?>
The above code will give the following output:
dlroW olleH nuf si gnimmargorP gnirts siht esreveR
Method 4: Using built-in function - strrev()
The PHP built-in function strrev() can also be used to reverse a string. Consider the example below:
<?php echo strrev("Hello World")."\n"; echo strrev("Programming is fun")."\n"; echo strrev("Reverse this string")."\n"; ?>
The above code will give the following output:
dlroW olleH nuf si gnimmargorP gnirts siht esreveR
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