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By Umesh Singh
Last update: 05 May 2020, 25 Questions
Introduction to PHP Strings

A string is basically a collection of characters. It is a data type in PHP. A function in PHP is a unit of code that returns a value based on an input or parameter and processing based on the codes.

Functions are basically a set of in a string that is used to manipulate this data type for different uses and requirements. Common PHP String functions include strrev(), strpos(), str_replace() and many more. The basic need of a string function is to help in completing specific tasks relating to a string. It could be reversing, replacing or even searching for text within strings.

PHP String functions are used to manipulate strings in order to perform a specific task/function when the user has given input. This is one of the most commonly used functions in PHP and if you are aspiring for a job as an SDE in PHP, learning string functions is a must.

Below is a list of the most commonly asked interview questions regarding String functions in PHP. Have a look or even download it in PDF format to read it later.

Most Frequently Asked PHP Strings

1. How to repeat a string to a specific number of times in php?

In PHP, the str_repeat() function, which is inbuilt is used to repeat a string for a specific number of times. This str_repeat() function creates new strings by repeating the given string ‘n’ number of times as specified.

Here is the syntax of the str_repeat() function: str_repeat(string, repeat)

Example

                                                    

Here is an example demonstrating the same:
echo str_repeat("BIQ ", 2);

Output

BIQ BIQ

2. List the most commonly use string functions in PHP?

Here is a list of the most commonly used PHP String Functions while programming:

  • substr() function: This function is used in PHP to give you access to a substring having a specific start and endpoints within the string.
    Syntax:
    string substr(string string, int start[, int length] );
  • strlen() function: This function is used in PHP to check the character length of a string.
    Syntax:
    echo strlen(“string”)
  • str_replace() function: This function is used in PHP as a find and replace function within any string.
    Syntax: str_replace ( mixed $search , mixed $replace , mixed $subject [, int &$count ] ) : mixed
  • trim() function: This function is used in PHP to trim all the whitespace from the starting point to the endpoint in any
    string.
    Syntax: trim ( string $str [, string $character_mask = " \t\n\r\0\x0B" ] ) : string
  • strpos() function: This function is used in PHP to find the first occurrence of a substring within a string.
    Syntax: strpos ( string $haystack , mixed $needle [, int $offset = 0 ] ) : int
    In the above syntax, it actually commands PHP to find the first occurrence of the substring needle in the string haystack.
  • strtolower() function: This function is used in PHP to convert all the characters in a string to lowercase.
    Syntax: strtolower ( string $string ) : string
  • strtoupper() function: Well, obviously this function is used to convert all the characters in a string to the upper case.
    Syntax: strtoupper ( string $string ) : string

In the above command, it returns with part of the haystack string starting from the point of the needle to the end of the haystack.

3. How to remove HTML tags from a string using PHP?

Here is an example to show how to strip the HTML tags from a PHP string.

Example

                                                    

$text = '<p>Test paragraph.</p><a href="#fragment">Other text</a>';
echo strip_tags($text, '<p><a>');

Output
Test paragraph.

4. What is the difference between print and echo in php?

The echo and print are basically the same functions, display output data on the screen. However, there are some minor differences between the two such as:

Echo Print
It has no return value. It has a return value of 1, hence can be used in expressions.
It can work with multiple parameters. It can function with only one argument at a time.
It is a bit faster than Print A bit slower than Print.

Here’s an example of each Echo and Print to clearly demonstrate their proper usage:

Example

                                                    
Echo

echo "PHP is Fun!";

Print

print "PHP coding is Fun!";

5. What is String in PHP?

In PHP, String is a collection of characters. It is one of the data types. We can declare variable and assign string characters to it and we can directly use them with echo statement.

Example

                                                    

$var1 = “This is good interview Question”
echo $var1;

6. How to calculate the length of a string?

We can calculate the length of a string with strlen() function in PHP.

$var1 = “This is good interview Question”;
echo strlen($var1);

7. What is the use of strpos in PHP?

strops() method is used to get the position of the first occurrence of a string inside another string.

Example

                                                    

$mainString = 'Best Interview Question';
echo strpos($mainString, "Interview");
// OUTPUT : 5

8. What is a substring in PHP?

substr() is a substring of PHP. It is an inbuilt function which is used to extract a part of the string.

9. What is TRIM function in PHP?

trim() removes all blank spaces or whitespace or other (specified) characters from both sides of a string.

$var = “ Best Interview Questions ”
echo $var;

Types:
  • ltrim() – It removes whitespace/other specified characters from the left side of a string.
  • rtrim() - It removes whitespace/other specified characters from the right side of a string.

Example

                                                    

$var = “Best Interview Questions”;
ltrim(“Best”, $var);
rtrim(“Questions”, $var);

10. How to replace a text in a string with another text in php?

We can use str_replace() method to replace a text in a string with another string.

Example

                                                    

str_replace("interview","interviews","Best interview questions!");

11. How to convert a string to uppercase in php? We can use strtoupper() method to convert any string to Uppercase.

Example

                                                    

strtoupper("Best Interview Questiomns");
// Output: BEST INTERVIEW QUESTIONS

12. How to insert a line break in php string?

You can use nl2br() to insert line break in the string.

Example

                                                    

nl2br("Best Interview \n Questions");

13. How to count a number of words in a string in php?

In PHP, we should use the str_word_count() function to count the number of words in a string.

Here’s its syntax: str_word_count ( $string , $returnVal, $chars )

To calculate the number of words in a string, use the function in the following way:

Example

                                                    

mystring = "This is a function";
print_r(str_word_count($mystring));

14. How to get the position of the character in a string in php?

To find the position of a character inside a string in PHP, use the strpos() function in the following way:
$pos = strpos($string, $char);

15. How to convert a string to lowercase in php?

You can use strtolower() to convert any string to lowercase.

Example

                                                    

strtolower('Best Interview Questions');
// OUTPUT: best interview questions

17. How to limit string length in php?

To limit the characters in a PHP string, use the following code:

if (strlen($str) > 10)
    $str = substr($str, 0, 6) . '...';

In the above code, if the str value is greater than 10, the output will display the final result from 0 to the 6th character of the said string.

18. How to read each character of a string in php?

For this, the str_split() function can be used. It will convert your string into an array of individual characters where you can enter the start and endpoint of the characters you wish to see.

Example

                                                    

$str = "Hello";
$arr1 = str_split($str);
print_r($arr1);

Output:

Array
(
[0] => H
[1] => e
[2] => l
[3] => l
[4] => o
)