PHP equivalent for Python's repr() [duplicate]

Question

I'm creating a simple array wrapper class and want it's __toString() method to be formatted like a Python list, eg: ["foo", "bar", 6, 21.00002351]. Converting each element to a string is not enough, since string-objects are actually enquoted in the list-representation.

Is there a repr() equivalent in PHP, and if not, what would a PHP implementation look like?

Cunning

php.net/manual/en/function.print-r.php – Protection

@DietrichEpp: This needs to be encapsulated in ob_start() and ob_end_clean(), but I'll use that for now. – Cunning

You should use a debugger instead anyway. – Exodontist

@NiklasR - uh no, print_r does not need ob_start etc -- just specify the second parameter and it will output to a variable. This feature was added in PHP 4.3, so if you think it needs ob_start, you're about ten years behind the times. But in any case, if it's just arrays of strings and numbers you want to output, I'd go with the json_encode answer; it's a closer fit to the output in your question. – Doing

I make one for PHP string cause var_export not working for string.here – Lodgment

Answer 1

Python's repr() returns an output where

eval(repr(object)) == object

Called by the repr() built-in function and by string conversions (reverse quotes) to compute the “official” string representation of an object. If at all possible, this should look like a valid Python expression that could be used to recreate an object with the same value (given an appropriate environment).

So the closest thing in PHP would be

• var_export — Outputs or returns a parsable string representation of a variable

The keyword here is parseable. While functions print_r and var_dump will give a certain representation of the data passed to them, they are not easily parseable, nor do they look like PHP expression, which could be eval'd.

Example:

var_export(['foo', 'bar', 1,2,3]);

will give

array (
  0 => 'foo',
  1 => 'bar',
  2 => 1,
  3 => 2,
  4 => 3,
)

and that is perfectly valid PHP code:

$data = ['foo', 'bar', 1, 2, 3];
$repr = var_export($data, true);

// have to use it with return though to eval it back into a var
$evald = eval("return $repr;");

var_dump($evald == $data); // true

Another option would be to use serialize to get a canonical and parseable representation of a data type, e.g.

$data = ['foo', 'bar', 1, 2, 3];
$repr = serialize($data); 
// -> a:5:{i:0;s:3:"foo";i:1;s:3:"bar";i:2;i:1;i:3;i:2;i:4;i:3;}
var_dump( unserialize($repr) == $data ); // true

Unlike var_export, the resulting representation is not a PHP expression, but a compacted string indicating the type and it's properties/values (a serialization).

But you are likely just looking for json_encode as pointed out elsewhere.

Making this a Community Wiki because I've already answered this in the given dupe.

Russophobe

Answer 2

I don't know Python but PHP arrays can contain any data type and nesting levels. I don't know how that translates into your format.

There're many functions to print an array:

• print_r()
• var_dump()
• var_export()

... but your format reminds me of JSON so you can simply do this:

<?php

$foo = array (
  'foo',
  'bar',
  6,
  21.00002351,
);
echo json_encode($foo); // ["foo","bar",6,21.00002351]

Of course, it's by no means automatic, i.e., this won't trigger any toString() method at all:

echo $foo; // "Array" + PHP Notice:  Array to string conversion

Marolda