Pretty Pprint

Callable pretty-printer for PHP arrays with Python-like formatting. PrettyPrint is a small, zero-dependency PHP utility that formats arrays in a clean, readable, PyTorch-inspired style. It supports aligned 2D tables, summarized tensor views, and flexible output options – making it ideal for ML experiments, debugging, logging, and educational projects.

Installation

composer require apphp/pretty-print

Usage

Note: When used in web (non-CLI) environments, output is automatically wrapped in <pre> to preserve spacing. In CLI, no wrapping is applied.

Global helper functions

Print scalars/strings

pprint('Hello', 123, 4.56);            
// Hello 123 4.5600

Print multiple 1D rows aligned as a 2D table

pprint([1, 23, 456], [12, 3, 45]);
// [[ 1, 23, 456],
//  [12,  3,  45]]

Label + 2D matrix

pprint('Confusion matrix:', [[1, 23], [456, 7]]);
// Confusion matrix:
// [[  1, 23],
//  [456,  7]]

2D tensor-style formatting

$matrix = [
    [1,2,3,4,5],
    [6,7,8,9,10],
    [11,12,13,14,15],
];
pprint($matrix);
// tensor([
//   [ 1,  2,  3,  4,  5],
//   [ 6,  7,  8,  9, 10],
//   [11, 12, 13, 14, 15]
// ])

Custom label instead of "tensor"

pprint($matrix, label: 'arr');
// arr([
//   [ 1,  2,  3,  4,  5],
//   [ 6,  7,  8,  9, 10],
//   [11, 12, 13, 14, 15]
// ])

2D tensor-style formatting with summarization

$matrix = [
    [1, 2, 3, 4, 5],
    [6, 7, 8, 9, 10],
    [11, 12, 13, 14, 15],
    [16, 17, 18, 19, 20],
    [21, 22, 23, 24, 25],
];
pprint($matrix, headRows: 2, tailRows: 1, headCols: 2, tailCols: 2);
// tensor([
//   [ 1,  2, ...,  4,  5],
//   [ 6,  7, ...,  9, 10],
//   ...,
//   [21, 22, ..., 24, 25]
// ])

3D tensor with head/tail blocks (PyTorch-like)

$tensor3d = [
    [[1, 2, 3],[4, 5, 6]],
    [[7, 8, 9],[10, 11, 12]],
    [[13, 14, 15],[16, 17, 18]],
];
pprint($tensor3d, headB: 1, tailB: 1, headRows: 1, tailRows: 1, headCols: 1, tailCols: 1);
// tensor([
//  [[1, ..., 3],
//   [4, ..., 6]],
//
//  ...,
//
//  [[13, ..., 15],
//   [16, ..., 18]]
// ])

Postfix and prefix control

// No newline at the end (like Python's end="")
pprint('Same line', end: '');
// Added newline at the end after printing
pprint('Add line');
pprint('Add line', end: "\n");
// Added addedional 2 newlines at the end after printing
pprint('Add 2 lines', end: "\n\n");

// Add a prefix at the start of the printed string
pprint('Tabbed', start: "\t");
// Combine with end to avoid newline
pprint('Prompted', start: '>>> ', end: '');

// Custom separator between multiple values (default is a single space " ")
pprint('A', 'B', 'C', sep: ', ', end: '');
// A, B, C

// Separator can also be provided via trailing options array
pprint('X', 'Y', ['sep' => "\n", 'end' => '']);
// X
// Y

Print and then exit the script

ppd('Fatal error');

As an object

use Apphp\PrettyPrint\PrettyPrint;

$pp = new PrettyPrint();
$pp('Hello', 42);       // same as pprint('Hello', 42)

$tensor3d = [
    [[1, 2, 3],[4, 5, 6]],
    [[7, 8, 9],[10, 11, 12]],
    [[13, 14, 15],[16, 17, 18]],
];

// Named options are supported
$pp($tensor3d, headB: 2, tailB: 1, headRows: 1, tailRows: 1, headCols: 1, tailCols: 1);

// Label + 2D
$pp('Metrics:', [[0.91, 0.02], [0.03, 0.88]]);

Running tests

# install dev dependencies
composer install

# run test suite
composer test

# run tests with coverage (requires Xdebug or PCOV)
composer test:coverage

Notes:

• Coverage drivers: You need Xdebug (xdebug.mode=coverage) or PCOV enabled for coverage reports. Without a driver, PHPUnit will warn and exit non‑zero.
• You can also run PHPUnit directly: vendor/bin/phpunit.

Options reference

• start: string. Prefix printed before the content. Example: pprint('Hello', ['start' => "\t"]).
• end: string. Line terminator, default to new line. Example: pprint('no newline', ['end' => '']);
• sep: string. Separator between multiple default-formatted arguments. Default is a single space ' '. Examples: pprint('A','B','C', sep: ', ', end: '') or pprint('X','Y', ['sep' => "\n", 'end' => '']).
• label: string. Prefix label for 2D/3D formatted arrays, default tensor. Example: pprint($m, ['label' => 'arr']).
• precision: int. Number of digits after the decimal point for floats. Example: pprint(3.14159, precision: 2) prints 3.14.
• headB / tailB: ints. Number of head/tail 2D blocks shown for 3D tensors.
• headRows / tailRows: ints. Rows shown per 2D slice with ellipsis between.
• headCols / tailCols: ints. Columns shown per 2D slice with ellipsis between.

All options can be passed as:

• trailing array: pprint($m, ['headRows' => 1, ...])
• named args (PHP 8+): $pp($m, headRows: 1, ...)

Defaults

• label: tensor
• sep: ' '
• precision: 4
• headB / tailB: 5
• headRows / tailRows: 5
• headCols / tailCols: 5

Limits

• precision: max 10
• headB / tailB / headRows / tailRows / headCols / tailCols: max 50
• label: max length 50 characters (longer labels are truncated)
• positional args (MAX_ARGS): up to 32 positional args are accepted; extras are ignored.

Positional policy:

• First arg can be a string label, number, or array.
• Exactly two positional args are allowed only for string label, array.
• Named/trailing options are applied only when the first arg is an array.