Chlef-Biostat-2026 is a self-contained trilingual (Arabic / French / English, RTL-aware) data-collection web platform for a cross-sectional study on adolescent overweight in the Wilaya of Chlef, Algeria (n = 1220, ages 14-19, academic year 2025-2026). The analytic engine is provided by the separately-distributed biostat-php Composer library (touilelhadj/biostat-php), which implements descriptive, bivariate and multivariate statistical methods (logistic regression, GLMM by PQL, GEE, MICE with Rubin's pooling, VIF, Box-Tidwell, Benjamini-Hochberg FDR) in pure PHP without dependency on R or SPSS. If you use this software, please cite it using the metadata from this file.