Explain the difference between echo, print, print_r(), and var_dump().

In PHP, echo, print, print_r(), and var_dump() are all used to output data, but they serve different purposes and behave differently. Let’s go step by step:

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1. echo

• Type: Language construct (not a function).
• Purpose: Outputs one or more strings.
• Return value: No return value.
• Usage: Can take multiple parameters separated by commas.
• Example:

echo "Hello, World!";
echo "Hello", " ", "World!";

• Notes: Fastest way to output strings. Cannot return a value, so can’t be used in expressions.

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2. print

• Type: Language construct (similar to echo).
• Purpose: Outputs a string.
• Return value: Returns 1, so it can be used in expressions.
• Usage: Only takes one argument.
• Example:

print "Hello, World!";
$result = print "Hello"; // $result will be 1

• Notes: Slightly slower than echo but can be used in expressions because it returns a value.

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3. print_r()

• Type: Function.
• Purpose: Prints human-readable information about a variable, especially arrays and objects.
• Return value: Returns true if output succeeds (or 1 in older versions) but can return output as a string if second parameter is true.
• Usage: Mostly used for debugging.
• Example:

$arr = [1, 2, 3];
print_r($arr);

Output:

Array
(
    [0] => 1
    [1] => 2
    [2] => 3
)

• Notes: Good for quickly checking arrays or objects in a readable format. Less detailed than var_dump().

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4. var_dump()

• Type: Function.
• Purpose: Dumps detailed information about a variable including its type and value.
• Return value: None.
• Usage: Mostly for debugging purposes.
• Example:

$arr = [1, 2, 3];
var_dump($arr);

Output:

array(3) {
  [0]=>
  int(1)
  [1]=>
  int(2)
  [2]=>
  int(3)
}

• Notes: Best for debugging because it shows type, length, and value. Works on any variable type.

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Summary Table

Feature	echo	print	print_r()	var_dump()
Type	Language construct	Language construct	Function	Function
Takes multiple args	Yes	No	No	No
Returns value	No	1	true/string	None
Shows type	❌	❌	❌ (only structure)	✅
Best for	Simple output	Simple output, expressions	Arrays/objects debugging	Detailed debugging

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✅ Key takeaway:

• Use echo for simple string output.
• Use print if you need a return value.
• Use print_r() for readable arrays/objects.
• Use var_dump() for detailed debugging with type info.