Why Does PHP Throw a 'Warning: A Non-numeric Value Encountered' Error?

"Warning: A Non-Numeric Value Encountered" - Uncovering the PHP Pitfall

In the world of PHP, every developer encounters roadblocks along their coding journey. One such obstacle is the perplexing "Warning: A non-numeric value encountered."

Let's delve into the depths of this error and illuminate its enigmatic nature.

The Issue at Hand

Upon transitioning to PHP 7.1, a developer was startled by an unexpected error message: "Warning: A non-numeric value encountered in on line 29." Analyzing the problematic line revealed the following:

$sub_total += ($item['quantity'] * $product['price']);

Intriguingly, this line of code functioned flawlessly on the developer's local environment. However, on the live server, it triggered the mysterious error.

Unveiling the Culprit

While the error message alluded to a non-numeric value, the source code appeared to handle numerical operations only. Seeking enlightenment, the developer scrutinized the underlying cause more meticulously.

After extensive investigation, a surprising revelation emerged: the developer had inadvertently concatenated two strings using the " " operator instead of the "." operator. This coding misstep, though seemingly innocuous, led to the erroneous warning message.

Resolving the Enigma

Embracing the lessons learned, the developer meticulously reviewed their code, ensuring that all strings were correctly concatenated using the "." operator. With this modification, the elusive error vanished, restoring harmony to their PHP adventure.

The key takeaway from this experience is the subtle yet crucial distinction between string concatenation ("." operator) and addition (" " operator) in PHP. This knowledge empowers developers to navigate the coding landscape with confidence, ensuring their applications function flawlessly.

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