A string is a data type used in programming to represent a sequence of characters. These characters can be letters, numbers, spaces, symbols, etc. In many programming languages, a string is enclosed in single quotes (') or double quotes (").

String Concatenation
Concatenation is the process of joining two or more strings together.

Here, the . operator is used to concatenate the variables $name and $lastname, separated by a space.

Size of a String
To find out the number of characters in a string, we use the strlen() function.

The strlen() function counts the number of characters, including spaces and punctuation.

Replacing Part of a String
The str_replace() function replaces all occurrences of a substring within a string.

Here, the word "apples" was replaced with "bananas" in the original string.

Convert to Uppercase or Lowercase
You can use strtoupper() to convert a string to uppercase and strtolower() to convert it to lowercase.

These functions are useful for standardizing the format of a string.

Get Part of a String
To extract part of a string, we use the substr() function.

Here, the substr() function starts at position 9 (index 0) and returns 3 characters from there.

Remove Whitespace from the Beginning and End
The trim() function removes whitespace (or other characters) from the beginning and end of a string.

This function is useful for cleaning strings received from forms or user input.

Break a String into an Array
The explode() function transforms a string into an array based on a delimiter.

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Here, the explode() function splits the string into several parts, using the comma as the delimiter.

Join Elements of an Array into a String
The implode() function does the reverse of explode(), joining the elements of an array into a string.

Find Position of Substring
The strpos() function returns the position of the first occurrence of a substring within a string.

If the substring is not found, the function will return false.

Reverse a String
To reverse a string, you can use strrev().

You can run the code at https://onecompiler.com/php